resolver

Controlled Modification of Metal-Organic
Frameworks at Metal Sites:
Local Environment Study and Properties
Dissertation
Wenhua Zhang

Controlled Modification of Metal-Organic
Frameworks at Metal Sites:
Local Environment Study and Properties
Dissertation
to obtain the doctorate Dr. rer. nat.
of the Faculty of Chemistry and Biochemistry
Ruhr‐University Bochum
Submitted by Wenhua Zhang, M. Sc.
July 2016

This thesis is based on the work performed during the time of October
2012 and July 2016 under the supervision of Prof. Dr. Roland A. Fischer
at the Chair of Inorganic Chemistry II, Organometallic & Materials, of the
Ruhr‐University Bochum.
1 st referee: Prof. Dr. Roland A. Fischer
2 nd referee: Prof. Dr. Nils Metzler‐Nolte
Herein I declare that I have written this thesis independently and
without unauthorized help. Further, I assure that I have used no other
sources, auxiliary means or quotes than those stated. I further declare
that I have not submitted this thesis in this or in a similar form to any
other university or college. Besides, I declare that I have not already
undertaken an unsuccessful attempt to obtain a doctorate from another
college or university.
Wenhua Zhang
July 2016

Acknowledgements
First of all, I sincerely appreciate my supervisor
Prof. Dr. Roland A. Fischer
for giving me the opportunity to study in the group of Inorganic Chemistry II at Ruhr-
University Bochum. I am grateful to him for affording me guidance and motivation on the
scientific research. Besides, I thank his support for allowing me to attend the international
conferences and visit the world-class research group, which open my mind and give me
much inspiration in scientific field as well.
I also thank Prof. Dr. Nils Metzler-Nolte for accepting to be the co‐referee of this
dissertation.
Further I would like to thank Dr. Zhenlan Fang for bringing me to the topic of Cu-based
DEMOFs and her help on this topic.
I address very special thanks to Dr. Olesia Halbherr for introducing me to the world of the
challenging project on Ru-based (DE)MOFs and for having been advising me during my
study on this topic. Thanks very much for your patience, your assistance and your
knowledge on the topic as well as your invaluable guidance on writing reports. I cannot
make so much progress without you.
Furthermore, I would like to thank the following persons without whom this work is not
able to be accomplished:
Dr. Kira Khaletskaya, Dr. Min Tu, Dr. Harish Paralla, Suttipong Wannapaiboon,
Christoph Rösler, and Inke Schwedler for collecting powder X-ray diffraction
patterns.
Dr. Arik Puls, Dr. Kerstin Freitag, Dr. Sebastian Henke and Manuela Winter for
conducting single‐crystal X‐ray experiments and helping me solve the singlecrystal
structure.
Andreas Schneemann for teaching me to perform the TG measurements.
Dr. Yuemin Wang (Karlsruhe Institute of Technology), Max Kauer, and Penghu Guo
(Laboratory of Industrial Chemistry, Prof. Dr. Martin Muhler, Ruhr‐University

Bochum) for the study of XPS and UHV-FTIR and providing the corresponding
figures.
Dr. Bauke Albada and Martin strack for carrying out the HPLC measurements
(Chair of Inorganic Chemistry I - Bioinorganic Chemistry, Prof. Dr. Nils Metzler‐
Nolte, Ruhr‐University Bochum).
Noushin Arshadi (group of Prof. Dr. Martin Muhler, Ruhr‐University Bochum) for
collecting the N2 sorption isotherms.
Dr. Rolf Neuser (Faculty of Geosciences, Institute of Geology, Mineralogy and
Geophysics, Ruhr‐University Bochum) for the gold coating on the non-conducting
SEM samples.
Dr. Kira Khaletskaya and Stefan Cwik for conducting SEM-EDX measurements.
Dr. Christian Wiktor for collecting TEM-EDX spectra.
Dr. Christian Sternemann (and Andreas Schneemann, Suttipong Wannapaiboon)
for helping me to gather X‐ray diffraction patterns at the DELTA facility. Ralph
Wagner (and Andreas Schneemann) for assistance of performing XAS on the Ru-
(DE)MOF samples and for introducing me to the study of XANES.
Karin Bartholomäus for elemental analysis.
Prof. Dr. Jeffrey R. Long for the chance to have a research stay in his group, at the
Department of Chemistry, University of California, Berkeley (USA). The whole
group for an inspiring communication and very nice time during my stay. I address
many thanks to Miguel Gonzalez for guiding me on conducting the catalytic
reaction in Chapter 4 and assistance on evaluating the data. Last but not the least,
Dianne Xiao, Douglas Reed, Julia Oktawiec for their great assistance with sorption
studies and help on collecting sorption isotherms.
Dr. Francesc X. Llabrés i Xamena (Institute of Chemical Technologies, Polytechnical
University of Valencia, Spain) for the collaboration and Konstantin Epp (group of
the Prof. Dr. Roland A. Fischer in Technical University of Munich) for performing
the catalytic reaction in Chapter 4.
Zhihao Chen and Majd Al-Naji (group of Prof. Dr. Roger Gläser, University of
Leipzig) for carrying out the catalytic reaction in Chapter 5 and the assistance on
study the catalytic activity.
I also want to acknowledge the financial support from China Scholarship Council to my
whole Ph.D study and Research School Plus at Ruhr-University Bochum for the funding of

attending conferences, my research stay at UC Berkeley and my invitation of Dianne Xiao
(from UC Berkeley) for the short visit in ACII group.
I am thankful to the master students who work with me during my Ph.D study: Marco
Rehosek, Sebastian Kunze, and Konstantin Epp.
I am grateful to all ACII members for a nice working atmosphere, the great team spirit and
inspiring communications, especially the former and present MOF family. The memorable
and wonderful time we spend together in the MOF 2014 conference and the trip in Japan
with our MOF guest Takashi Toyao. I express my many thanks to Dr. Christian Wiktor on
teaching me skills for my first poster. Also further thanks to Dr. Chuanqiang Li, Suttipong
Wannapaiboon, Andreas Schneemann, and Konstantin Epp for the kind accompany
during XAS data collecting in DELTA facility.
Besides, I address many thanks to my lab neighbor Dr. Raghavender Medishetty and Dr.
Arik Puls for the abundant and fruitful discussions.
I would like to express my thanks to Dr. Mariusz Molon for affording technical help on my
computer, and OM group members for sharing the experience on air-free synthesis.
I am grateful to Uschi Hermann for her kindness and great help in the lab.
Furthermore, I would like to express my thanks to Jana Weiing, Andreas Schneemann,
Jiyeon Kim, Inke Schwedler and Dr. Christian Wiktor for the great time during ACS fall
meeting and the nice trip in Boston.
I would like to express my warm thanks to Sabine Pankau and Jacinta Essling for their
great help with administrative issues.
Many thanks to my office colleagues for nice working atmosphere, giving me suggestions
and help on the daily life and as translators: Sarah Karle, Mathies Evers, Stefan Cwik,
Maximilian Gebhard, Inke Schwedler, Richard O'Donoghue, Jiyeon Kim, Andreas
Schneemann, Dr. Christian Wiktor, Dr. Arik Puls, and Dr. Sun Ja Kim.
I am also thankful to Dr. Ke Xu for helping me go through a bunch of documents to settle
down in Germany.
Last but the most important, I would like to deeply thank my parents Denggao Zhang and
Chunying Wu, for giving me the freedom and support to study abroad and their endless
love and motivation during my studies. Also thank my siblings, Wenjing and Wenbo

Zhang, for their continuous support and care. My love and deep appreciation to Zhihao
Chen for always being at my side. His motivation and continuous care help me recover
from the sadness of homesick and overcome the challenging in my life and study. All these
would not happen without them.

Table of Contents
Table of Contents ................................................................................................................................................. I
Abbreviations ....................................................................................................................................................... V
1 Motivation .................................................................................................................................................... 1
2 General introduction ............................................................................................................................... 3
2.1 Origin of MOFs - Coordination polymers ............................................................................... 3
2.2 Definition, Chemistry and features of MOFs ........................................................................ 7
2.2.1 Definition and nomenclature of MOFs ................................................................ 7
2.2.2 MOF features .................................................................................................................. 8
2.3 Synthetic approaches, modification and applications of MOFs ................................ 14
2.3.1 Traditional synthesis approaches ...................................................................... 14
2.3.2 Reticular synthesis ................................................................................................... 15
2.3.3 Way to the modification of MOFs ....................................................................... 16
2.3.4 Application of MOFs ................................................................................................. 23
3 Controlled secondary building unit approach to the formation of the
isostructural Ru II,II and Ru II,III analogs of [M3(BTC)2]n ........................................................... 26
3.1 Preparation and investigation of the Ru II,III -analogs of [M3(BTC)2]n ...................... 28
3.1.1 The family of [M3(BTC)2]n...................................................................................... 28
3.1.2 Background and the state-of-the-art in research on Ru-analogs of
[M3(BTC)2]n.................................................................................................................. 29
3.1.3 [Ru3(BTC)2Yy]n·G g obtained by CSA using [Ru2(OOCR)4X] and
[Ru2(OOCCH3)4]A: synthesis and characterization ..................................... 31
3.1.4 Pre-activation by solvent exchange ................................................................... 37
3.1.5 Study of [Ru3(BTC)2Yy]n·G g after solvent exchange .................................... 38
3.1.6 Summary ....................................................................................................................... 48
3.2 Elaboration of Ru II,II analog of [M3(BTC)2]n........................................................................ 50

II
3.2.1 Synthesis and characterization of SBU-e and Ru-MOF 5.......................... 50
3.2.2 Investigation on the Ru oxidation state and porosity of Ru-MOF 5 .... 53
3.2.3 Conclusions .................................................................................................................. 55
4 Linker-based MOF solid solutions: Defect-Engineered MOFs (DEMOFs) .................... 56
4.1 Introduction .................................................................................................................................... 58
4.1.1 Solid solutions ............................................................................................................ 58
4.1.2 Defects in MOFs and its “engineering”............................................................. 60
4.2 Ruthenium Metal-Organic Frameworks featuring Different Defect Types ......... 65
4.2.1 Synthesis and characterization of the Ru-DEMOF materials ................. 65
4.2.2 Porosity of Ru-DEMOF samples and the confirmation of the DL
incorporation .............................................................................................................. 76
4.2.3 XANES, XPS and UHV-FTIR studies: ruthenium oxidation state
variation as indication of defect type formation ......................................... 79
4.2.4 CO2, CO and H2 sorption properties of Ru-DEMOFs ................................... 91
4.2.5 Catalytic test reactions ......................................................................................... 100
4.2.6 Conclusions ............................................................................................................... 106
4.3 Defects Engineering in [Cu3(BTC)2]n: Effect of the synthetic parameters ......... 108
4.3.1 Preparation and characterization of Cu-DEMOF samples
[Cu3(BTC)2-x(ip)x]n.................................................................................................. 109
4.3.2 Composition and porosity of the prepared Cu-DEMOFs ....................... 116
4.3.3 Oxidation state(s) of metal-sites in prepared Cu-DEMOFs .................. 119
4.3.4 Conclusions ............................................................................................................... 121
5 Simultaneous introduction of various palladium active sites into MOF via onepot
synthesis: Pd@[Cu3-xPdx(BTC)2]n ......................................................................................... 122
5.1 Introduction on the selection of metal type in MOFs ................................................. 123
5.2 Preparation and Structure of the Cu/Pd-BTC_1-3 ....................................................... 126
5.3 Compositional characterization and sorption properties of the prepared
Cu/Pd-BTC_1-3 ........................................................................................................................... 130

III
5.4 Synthesis, compositional characterization and sorption properties of
Cu/Pd-BTC_4 ............................................................................................................................... 136
5.5 Catalytic test reaction .............................................................................................................. 143
5.6 Conclusions ................................................................................................................................... 146
6 Summary and Outlook ...................................................................................................................... 147
7 Experimental Section ........................................................................................................................ 150
7.1 General methods ........................................................................................................................ 150
7.1.1 X-ray Diffraction (XRD) ....................................................................................... 150
7.1.2 FT-IR spectroscopy ................................................................................................ 151
7.1.3 Nuclear Magnetic Resonance (NMR) Spectroscopy ................................ 153
7.1.4 Thermogravimetric analyses (TGA)............................................................... 154
7.1.5 Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray
spectroscopy (EDX)............................................................................................... 154
7.1.6 Transmission electron microscope (TEM) and EDX ............................... 154
7.1.7 Elemental Analysis / Atomic absorption spectroscopic (AAS) .......... 154
7.1.8 Gas Sorption ............................................................................................................. 155
7.1.9 X-ray absorption near edge structure (XANES)........................................ 157
7.1.10 X-ray photoelectron spectroscopy (XPS)..................................................... 158
7.1.11 High Performance Liquid Chromatography (HPLC) ............................... 158
7.1.12 Catalytic studies ...................................................................................................... 159
7.2 Experimental data on chapter 3........................................................................................... 160
7.2.1 Synthesis of the ruthenium precursors ([Ru2(OOCR)4X] and
[Ru2(OOCCH3)4]A).................................................................................................. 160
7.2.2 Synthesis of Ru-MOFs [Ru3(BTC)2Xx]·Gg ...................................................... 168
7.3 Experimental data on chapter 4........................................................................................... 173
7.3.1 Synthesis of Ru-DEMOF samples (1a-1d, 2a-2d, 3a-3d, 4a-4c) .......... 173
7.3.2 Catalytic reactions using Ru-DEMOFs as catalysts .................................. 177
7.3.3 Synthesis of [Cu3(BTC)2]n (Cu-BTC)............................................................... 177

IV
7.3.4 Synthesis of Cu-DEMOF samples (D1-8)...................................................... 178
7.4 Experimental data on chapter 5........................................................................................... 186
7.4.1 Synthesis of [Cu3-XPdx(BTC)2]n ......................................................................... 186
7.4.2 Hydrogenation of PNP to PAP ........................................................................... 190
7.5 Supplementary details in Outlook ...................................................................................... 192
8 Bibliography.......................................................................................................................................... 194
Appendix ........................................................................................................................................................... 205
List of Publications
List of Presentations
Curriculum Vitae

V
Abbreviations
4-btapa
5-Br-ip
5-Br-ipH2
5-NH2-ip
5-NH2-ipH2
5-OH-ip
5-OH-ipH2
AAS
AcO
AcOH
BBR
bdc
BET
bpy
BTC
BTT
CP
CPO
CSA
CUS
DEMOFs
DL
DMF
1,3,5-benzene tricarboxylic acid tris[N-(4-pyridyl)amide]
5-bromoisophthalate
5-bromoisophthalic acid
5-aminoisophthalate
5-aminoisophthalic acid
5-hydroxyisophthalate
5-hydroxyisophthalic acid
atomic absorption spectrascopy
acetate
acetic acid
building block replacement
1,4-benzenddicarboxylate
Brunauer-Emmett-Teller
bipyridine
1,3,5-benzenetricarboxylate
1,3,5-benzenetristetrazolate
coordination polymer
coordination polymer from Oslo
controlled secondary building unit approach
coordinatively-unsaturated metal sites
defect-engineered metal-organic framworks
defect linker
N,N-dimethylformamid

VI
DMSO
dobdc
e.g.
EA
EDX
EtOH
EXAFS
FT-IR
GC
H2ip
H2pydc
H3BTC
HKUST
HML
HPLC
i.e.
IML
ip
IRMOF
IUPAC
MC
mCUS
MeOH
MIL
MOF
dimethyl sulfoxide
2,5-dioxido-1,4-benzenedicarboxylate
exempli gratia (from latin = for example)
elemental analysis
energy-dispersive X-ray spectroscopy
ethanol
extended X-ray absorption fine structure
fourier transformation infrared (spectroscopy)
Gas chromatography
isophthalic acid
pyridine-3,5-dicarboxylic acid
1,3,5-benzenetricarboxylic acid
Hong Kong Unversity of Science & Technology
heterostructural mixed-linker
High performance liquid chromatography
id est (from Latin = it is, namely)
isostructural mixed-linker
isophthalic
isoreticular metal-organic framework
International Union of Pure and Applied Chemistry
mixed-component
modified coordinatively-unsaturated metal sites
methanol
Matériaux de l′Institut Lavoisier
metal-organic framework

VII
MTV
Mw
NMR
NP
PAP
PivO
PivOH
PNP
PSM
PW
PXRD
pydc
pyz
r.t.
redox
rion
SALE
SBET
SBU
SEM
STP
TEM
TGA
THF
TML
multivariate
molecular weight
nuclear magnetic resonance
nano-particle
p-aminophenol
pivalate
pivalic acid
p-nitrophenol
post-synthetic method
paddlewheel
powder X-ray diffraction
pyridine-3,5-dicarboxylate
pyrazine
room temperature
reduction-oxidation
ionic radii
solvent-assisted linker exchange
BET surface area
secondary building unit
scanning electron microscopy
standard temperature and pressure
transmission electron microscopy
thermal gravimetric analysis
tetrahydrofuran
truncated mixed-linker

VIII
TOF
UHV
UiO
UMCM
vs
WCA
XANES
XAS
XPS
ZIF
turnover frequency
ultra high vacuum
Universitetet i Oslo
University of Michigan Crystalline Material
versus
weakly coordinating anion
X-ray absorption near edge structure
X-ray absorption sepctroscopy
X-ray photoelectron spectroscopy
zeolitic imidazolate framework

1 Motivation
Looking through the essential fields in nature and in our daily life, one can find that porous
materials play an important role. For example, porous rocks can store water, petroleum
and natural gas. Activated carbon as a prominent example of porous materials have been
widely used in various applications involving purification of gas, gold and water, as well
as filters in gas masks and respirators, etc. Another famous example is zeolites, which are
broadly used as ion-exchange beds in domestic and commercial water purification and
softening, catalysts in oil tracking, etc.
As zeolite-like architectures, metal-organic frameworks (MOFs) represent a young class
of hybrid inorganic-organic crystalline porous materials, formed from organic linkers and
inorganic build blocks (metal nodes). Ability to tune the inorganic building blocks as well
as the diverse characteristics of the organic moieties featured in MOFs ensures its great
advantage in comparison with the conventional porous materials (e.g. zeolites and
activated carbons), which attracted huge attentions over last decades. Nowadays, MOFs
are also extensively investigated as porous materials promising for gas
storage/separation, sensing, drug delivery and catalysis, etc.
Various synthetic approaches applied to MOFs afford to achieve their rich diversity, high
level of complexity and functionality. For example, reticular synthesis (versatile design of
functionalized organic linkers), design of mixed-component MOFs via post-synthetic
modification (including metal and linker exchange), or mixed-linker/metal copolymerization
has attracted huge attention with this regard. To note, the coordinatively
unsaturated metal sites (CUS) in MOFs play a key role in many applications, especially in
enhanced catalytic activity and effective gas sorption/separation. Hence, increased
complexity by means of mixed-component MOFs can be combined with the generation of
defects around the metal centers, which could lead to more open metal sites, or in the case
of clustering of the point defects, mesoporous MOFs can be obtained. Thus, it comes to the
“so-called” defect-engineering MOFs (DEMOFs). This manner of advanced modification of
MOFs holds enormous potential to optimize the materials properties beyond the

2 Chapter 1
limitations of the (non-doped) parent MOFs. In particular, increased sorption capacity,
selectivity and enhanced catalytic activity could be expected. Up to date, only limited
reports have been dealing with the studies on DEMOFs and their application.
Among the MOFs featuring CUSs and showing good performance on applications, HKUST-
1 ([Cu3(BTC)2]n) is one of the widely and well investigated MOFs. Besides, its mixedvalence
structural analogue [Ru3(BTC)2Yy]n (Y = counter-ions, 0≤y≤1.5) exhibits sufficient
chemical and thermal stability, and can offer rich photo/redox chemistry. Hence, in this
thesis those two kinds of MOFs with the general formula [M3(BTC)2]n have been chosen
as candidates on the study of defect-engineering.
However, before starting with the exploration of such intriguing DEMOFs, the formation
of both “intrinsic” and “intentional” defects in MOFs should be wisely taken into account.
Especially, in the case of [Ru3(BTC)2Yy]n, due to the kinetic reason, its formation should be
carefully monitored. Hence, Chapter 3 in this thesis mainly focus on the parent
[Ru3(BTC)2Yy]n for the study of possible intrinsic defects, optimized exclusion of the guest
molecules and elaboration of mono-valence Ru analog of HKUST-1. Further, intentional
introduction of defects to [Cu3(BTC)2]n and [Ru3(BTC)2Yy]n respectively by linker and/or
metal doping will be worth investigating. Modifications of the metal sites, generation of
(additional) accessible coordination sites as well as the complexity of the developed
DEMOFs will be studied in detail in Chapters 4 and 5. Moreover, the impact of the defects
engineering on gas sorption and catalysis properties of the resulting DEMOFs will be
explored. It is expected that these study show a comprehensive picture on the DEMOF
derivatives of the selected M-BTC structure and give us deep insights on the defectengineering
of other MOFs.

2 General introduction
The aim of this chapter is to give a general introduction on the research progress of metalorganic
frameworks (MOFs) including the origin of MOFs, their chemistry, structural
features, synthetic approaches, modification on the structure as well as their applications.
2.1 Origin of MOFs - Coordination polymers
In 1833, J. J. Berzelius firstly use the term “polymer” to describe any compound that could
be formulated as consisting of multiple units of a basic building block. [1] Later, Werner for
the first time, proposed the correct structure [Co(NH3)6]Cl3 for coordination compounds
containing complex ions in 1893, which developed the groundwork for the study of
coordination polymers (CPs). In 1916, to define dimers and trimers of various cobalt(II)
ammine nitrates, the term “CPs” was firstly employed by Y. Shibata [2] and has been
continuously used in the scientific literature since the 1950's. Moreover, the first review
on CPs was published in 1964. [3] The International Union of Pure and Applied Chemistry
(IUPAC) Red Book of inorganic nomenclature from 2005 gives the following definition of
coordination compounds: “A coordination compound is any compound that contains a
coordination entity. A coordination entity is an ion or neutral molecule that is composed of
a central atom, usually that of a metal, to which is attached a surrounding array of atoms
or groups of atoms, each of which is called a ligand”. [4] Consequently, CPs can be
conceptually considered as coordination compounds with extended arrays structures of
one, two or three dimensions (Figure 2.1). [5] Typically, CP consists of two central
components: metal ions (serving as connectors) and ligands (serving as linkers). Apart
from these two components, blocking ligands, counter-anions, non-bonding guests or
template molecules can be also included (Figure 2.2). The number and orientation of the
binding sites (i.e. coordination numbers and geometries) are the important
characteristics of the connectors and linkers. Their combination in numerous ways via a
self-assembly enables the formation of practically an infinite number of CPs (Figure 2.1).

4 Chapter 2
For the synthesis of CPs, transition metals and lanthanides are often utilized as connectors.
According to the type of the metal and its oxidation state, coordination numbers can vary
from 2 to 7, resulting in a variety of coordination geometries such as linear, T- or Y-
shaped, tetrahedral, square-planar, square-pyramidal, trigonal-bipyramidal, octahedral,
trigonal-prismatic, pentagonal-bipyramidal and the corresponding distorted forms
(Figure 2.2). In addition, metal-complexes might be also used as connectors instead of
(naked) metal-ions. It has an advantage of offering the bond angles control and restricting
the number of coordination sites via “ligand-regulation” of a connector, where chelating
or macrocyclic ligands directly bound to a metal connector block the redundant sites and
the linkers are left free for specific sites. [6]
Figure 2.1. Schematic demonstration of the CP construction via the self-assembly of connector
(metal nodes) and the simplest linker (ligands) in 1-3D.
Figure 2.2. Components of CPs. Inspired by the report from Kitagawa, et al. [7]

Chapter 2 5
On the other hand, linkers provide various connecting sites with tuned binding strength
and directionality. Linkers utilized in the CP construction may be halides (F, Cl, Br and I),
CN - and SCN - ions, [8-9] cyanometallate anions ([M(CN)x] n- ) as well as neutral, anionic and
cationic organic ligands. Among all these ligands, halides as the smallest and simplest one
are broadly employed to form quasi-1D halogen-bridged mixed-valence compounds (MX
chains), which feature extensive physical properties. [10] Furthermore, halides can be well
incorporated along with neutral organic ligands in the coordination frameworks. [11]
Cyanometallate anions could perform various geometries, similar to the metal ions with
coordination number from 2 to 7 mentioned above. With respect to the neutral organic
ligands, pyrazine (pyz) and 4, 4’-bpy (bpy = bipyridine) are the most often used in the
reports. [12] As to the anionic ligands, di-, tri-, tetra- and hexacarboxylate molecules are
typically employed. [13-15] On the contrary, CPs with cationic ligands are not very common
due to their low affinity for cationic metal ions. [16-17]
The bonding interactions between connectors and linkers in the CPs are mainly
coordination bonds. Additional weak interactions such as hydrogen and metal-metal
bonds, π- π and CH- π, electrostatic and van der Waals interactions can also participate to
construct the structure of CPs. Consequently, both robust and flexible networks could be
made. Many CPs studied in the earlier stage (1 st generation) feature open voids, cavities
or channels which are usually occupied by the solvent molecules or counter-anions. Such
guests might be exchanged post-synthetically against other ions or solvents, what is of
highly interest to study (host-guest chemistry, ion-exchange, etc.). [18-19] However,
complete removal of the guests molecules in this type of polymers is accompanied with
an irreversible structure collapse, what considerably restrict their application in the fields
of gas storage and separation as a result of low structural rigidity and absence of
permanent porosity. On the other hand, structural interpenetrations, in which the voids
constructed by one framework are occupied by one or more other independent
frameworks, [20] frequently happens in chemistry of CPs and might facilitate formation of
robust structures. Providing structural rigidity, this way, however, often leads in
considerable reduction of the pore sizes and precludes creation of highly porous
frameworks. Therefore, in spite of the abundant study on this class of CPs (1 st generation)
in the early stage (before 1990s), synthesis of coordination networks exhibiting
permanent porosity was still an open question until the exploration of [Co2(4,4′-
bpy)3(NO3)4]n(H2O)4 in 1997 by S. Kitagawa. [21] This compound featuring channeling

6 Chapter 2
cavities is able to reversibly adsorb CH4, N2, and O2 in the pressure range of 1–36 atm
without deformation of the crystal framework.

Chapter 2 7
2.2 Definition, Chemistry and features of MOFs
2.2.1 Definition and nomenclature of MOFs
The IUPAC group recommends the following definition of MOFs: “A metal–organic
framework, abbreviated to MOF, is a coordination network with organic ligands containing
potential voids.” Moreover, the hierarchical terminology is also recommended, where the
most general term is CP, followed by the coordination networks acting as a subset of CPs
and MOFs, a further subset of coordination networks (Figure 2.3). [5] It is worth
mentioning that other terms like “porous CPs” or “porous coordination network”, which
have basically the same meaning as MOFs, are also present in many scientific publications.
In addition, another term “hybrid inorganic-organic material” was occasionally used for
MOFs, however is not recommended by the IUPAC group due to its imprecise description.
Owing to the cumbersome work, the systematic nomenclature of MOFs has not been given
yet. Nevertheless, assigning to some conceptually important compounds the trivial names
or nicknames in accordance with place of their origin followed by a number, such as
HKUST-1 (Hong Kong University of Science and Technology), MIL-53 (Matériaux de
l′Institut Lavoisier) and UiO-66 (Universitetet i Oslo), is also acceptable.
Figure 2.3. The hierarchical terminology of the CPs, coordination networks and MOFs based on
the recommendations of the IUPAC group.

8 Chapter 2
2.2.2 MOF features
Advantages of MOFs combining the features of CPs and porous solids
MOFs (i.e. porous coordination networks) could be considered like a combination of both
CPs and porous solids. As a subclass of CPs, MOFs feature even more diverse and robust
structures. The construction of MOFs is commonly realized by the connection of “rigid”
secondary building units (SBUs) rather than the simple linking of node and spacer in
coordination networks where usually single atoms are joined by ditopic linkers. On the
other hand, the feature of being microporous compounds, which is very important
motivation to design MOFs, should not be underrated. Classical porous solids including
zeolites, silica, alumina, carbon-based materials, etc. are known in various research fields
of not only chemistry but also physical and material science due to their versatile
application related to separation, storage and heterogeneous catalysis. For example,
zeolites can be effectively utilized as molecular sieves for adsorbent of gases and liquids,
builders for the production of laundry detergents, etc. Moreover, the usage of activated
carbon in air filters and gas masks is seen in our daily life. MOFs as a novel class of porous
solids are expected to behave in a similar manner as other mentioned porous solids. In
fact, they exhibit uniform pores or open channels which might be preserved upon careful
removal of the guest molecules. Compared to the CPs of 1 st generation, this essential
characteristic allows MOFs to hold huge potential for a wide variety of applications such
as gas sorption/separation, [22-23] gas storage [24-26] and catalysis, [27-29] for which previously
only conventional purely inorganic (e.g. zeolites, alumina, silica) or purely organic porous
solids (e.g. activated carbons) were suitable.
Features highlight 1 –Structure diversity and porosity
As mentioned above, MOFs are constructed from metal nodes (also known as inorganic
building blocks or SBUs) and multidentate organic linkers (e.g. carboxylates, [13, 30]
azolates, [31-33] etc.). One of the common clusters, the octahedral Zn4O(CO2)6 cluster(Figure
2.4) composed of four ZnO4 tetrahedra with a common vertex and six carboxylate C atoms
can be as SBUs and further joined together by the benzene links, which leads to a 3D MOF
Zn4O(bdc)3∙(DMF)8(C6H5Cl) (known as MOF-5, bdc = 1,4-benzenddicarboxylate, DMF =
N,N-Dimethylformamid), where the vertices are the octahedral SBUs and the edges are
the benzene struts. [18] The obtained framework exhibit high thermal stability(300 °C) and
porosity (Brunauer-Emmett-Teller (BET) surface area well above 3500 m 2 /g). The same

Chapter 2 9
inorganic SBU can be connected by distinct ditopic linkers to afford various materials with
the same structural topology (so-called IRMOFs) featuring predetermined cavity size and
functions (Figure2.5).[25, 34]
Figure 2.4. Construction of the MOF-5 framework. Top, the Zn 4 O(CO 2 ) 6 cluster. Bottom, one of the
cavities in the MOF-5 framework. Reprinted by permission from Macmillan Publishers Ltd:
Nature, 402, 276-279, copyright 1999. [18]
Consideration on the chemical and geometric attributes of the essential SBUs and linkers can
afford prediction of the framework topology, and subsequently result in the design and targeted
synthesis of a new class of porous materials featuring robust structures and high porosity.
Transition-metal carboxylate clusters may serve as SBUs with different points of extension
varying from 3 to 66. [30] In addition to the typical octahedral zinc acetate cluster (Zn 4 O(CO 2 ) 6 ) as
SBU, one of the other metal cluster commonly employed as a build blocks in the MOF synthesis is
square bimetallic PW (M 2 (CO 2 ) 4 ) (Figure 2.6), in which four carboxylates are connected to two
metal centers. Each metal center is often capped by labile solvent molecules (such as H 2 O). A
typical example composed of such building blocks is the 3D porous framework [Cu 3 (BTC) 2 ] n (also
known as HKUST-1 [35] or MOF-199 [36] ) reported by Chui. et al. in 1999.

10 Chapter 2
Figure 2.5. A series of isoreticular MOFs (IRMOFs). [34] Reprinted from Micropor. Mesopor.
Mater.,73, J. L. C. Rowsell, O. M. Yaghi, Metal–organic frameworks: a new class of porous materials,
3‐14. Copyright 2004, with permission from Elsevier.
Figure 2.6. Square PW cluster (M 2 (CO 2 ) 4 )with two terminal ligand sites (left) and the structure of
HKUST-1.
Features highlight 2-Flexibility

Chapter 2 11
Figure 2.7. a, Three classes of host materials categorized according to attributes of softness,
hardness (rigidity) and regularity. The overlapping zone of the two stages indicates materials
belonging to either of the ends. b, Classification of porous CPs into three categories. Reprinted by
permission from Macmillan Publishers Ltd: Nature Chemistry, 1, 695–704, copyright 2009. [37]
Besides features mentioned above (structural versatility and permanently porosity),
MOFs might also be flexible. Kitagawa et. al classified porous CPs into three generations
(Figure 2.7). [37-38] The 1 st generation, which have been earlier mentioned in this chapter,
represents porous coordination networks, which are comparably labile and collapse upon
removal of the guests from the pores. The 2 nd generation includes robust frameworks
exhibiting permanent porosity (reversible adsorption/desorption of guest molecules)
with complete preservation of the crystalline order. The 3 rd generation, identified as
flexible or dynamic porous frameworks, is able to undergo defined (and reversible) phase
transitions as a respond to such external stimuli as thermal, [39] , guest molecule
adsorption/desorption, [40] mechanical stress, [41] or light. [42] However, such structural
transitions do not lead to breaking of coordination bonds and the internal connectivity of

12 Chapter 2
the material is retained. Materials undergoing such kinds of phase transitions are often
called soft porous crystals. [37] The effect of large framework flexibility induced by specific
host-guest interaction is also known as “breathing”. [43] One of the best-studied flexible
systems is the MIL-53 system ([M(bdc)(OH)]n, M 3+ =Al 3+ , [44] Fe 3+ , [45] Cr 3+ , [46] Ga 3+ , [47]
In 3+ , [48] Sc 3+ , [49] ). These frameworks demonstrate different crystal phases according to the
activation state and the incorporation of guest molecules. Thus, after activation MIL-53
reveals a high-temperature phase with large pores (lp), which can shrinks to a narrowpore
phase (np) upon the adsorption of low amounts of polar molecules (Figure 2.8).
Moreover, a closed-pore phase was observed after activation of MIL-53(Fe) [45] and MIL-
53(Sc). [49] In addition to these famous MILs-53, some M2-PW based pillared-layered MOFs
also exhibit certain degree of flexibility upon guest adsorption. [50-52]
Figure 2.8.The different forms of MIL-53: (a) as synthesized (as); disordered terephthalic acid
molecules lie within the tunnels; (b) high temperature (open), lp; (c) room temperature hydrated
form (hydr.), np. Note the changes in the cell parameters during the thermal treatments
Reproduced from Chem. Soc. Rev., 2008, 37, 191-214 with permission of The Royal Society of
Chemistry. [53]
Features highlight 3-Good thermal stability even good chemical stability
Thermal stability of MOFs ranges from 250 °C to 500 °C. [25, 31, 54-55] . Chemically stable
MOFs, however, are challenging to be made due to their susceptibility to linkdisplacement
reactions under the treatment with solvents over extended periods of time.
Zeolitic imidazolate framework ZIFs, in particular ZIF-8 (Zn(MIm)2, MIm = 2-
methylimidazolate) is one of the prominent examples which reveals exceptional chemical
stability. [31] Remarkably, the structure integrity is retained after immersion ZIF-8 into
boiling methanol, benzene, or water for up to 7 days. Besides, its treatment in

Chapter 2 13
concentrated sodium hydroxide at 100°C for 24 hours does not alter the framework.
Another well-known example exhibiting high chemical stability is MOFs based on the
Zr(IV) cuboctahedral SBUs. In fact, high acid (HCl, pH = 1) and base resistance (NaOH, pH
= 14) of UiO-66 (Zr6O4(OH)4(bdc)6) and its NO2 - and Br - functionalized derivatives was
observed. [54-55] Furthermore, a structure of pyrazolate-bridged MOF (Ni3(BTP)2; BTP3 - =
4,4’,4’’-(benzene-1,3,5-triyl)tris(pyrazol-1-ide)) was fully preserved after treatment in
aqueous solutions within a wide pH value range (from 2 to 14) at 100 °C for 2 weeks. [56]
Thus, such MOFs featuring high chemical stability are promising to afford benefit of
enhancing their performance in carbon dioxide capture from humid flue gas, pave the way
of their applications to water-containing processes, etc.
To summarize, characteristic features of MOFs include (i) well-ordered porous structures
and designable channel surface functionalities, (ii) flexible, dynamic behavior in response
to guest molecules, and (iii) good thermal stability and (in some cases) also chemical
stability. It can be expected that the diverse chemistry of MOFs (i.e. huge variety of
inorganic SBUs and organic linkers bearing distinct functionalities) can result in a wide
range of different framework structures as well as in deliberate tuning of their properties,
which eventually leads to their applications in various fields.

14 Chapter 2
2.3 Synthetic approaches, modification and applications of MOFs
2.3.1 Traditional synthesis approaches
Figure 2.9. Overview of the synthetic methods applied to MOFs. Reprinted with permission from
N. Stock and S. Biswas, Chem. Rev., 2012, 112, 933-969. Copyright (2012) American Chemical
Society. [57]
As has been earlier mentioned, self-assembly of various metal ions and organic linkers
leads to a large variety of networks featuring high porosity. However, it should be noted,
that MOFs formation is also strongly affected by diverse synthetic parameters and
conditions, such as nature of metal-precursors along with structural characteristics of
linkers, concentration and stoichiometry of the employed reagents, usage of modulator,
kind of solvent(s) and pH of the reaction solution), heating source, reaction temperature,
time, pressure, etc. Figure 2.9 summarizes various synthetic approaches reported so far
for MOFs. Conventional methods imply usage of either room or elevated temperatures
and solvothermal/hydrothermal conditions (i.e. closed vessels under autogenous
pressure above the boiling point of the solvent [58] ) (Figure 2.9). In addition to typical
electric heating, other synthetic approaches such as microwave heating, electrochemical,
mechanochemical, ultrasonic methods have been also emerging(Figure 2.9) [57, 59] and
resulted in materials with various particle sizes and properties. High-throughput methods

Chapter 2 15
afford a good way to study synthesis of MOFs in a systematic way and under well-defined
conditions. Scaling-up of the synthesis on industrial-scale has been also achieved for
several MOFs. In particular, BASF produces Cu-BTC (Basolite ® C300), Fe-BTC (Basolite ®
F300), MIL-53 (Basolite ® A100), and ZIF-8 (Basolite ® Z1200), which are commercial
available through Sigma-Aldrich.
2.3.2 Reticular synthesis
Reticular chemistry is a commonly used synthesis approach in the earlier stage for the
versatile design of expansion of MOF structure to generate ultrahigh porosity and large
pore openings. [60] Isoreticular principle allows the vary of size and nature of a structure
while the underlying topology is kept. After the exploration of MOF-5, Yaghi et al. obtained
a series of isoreticular MOFs on the basis of MOF-5 (Figure 2.5). Indeed, one of these
compounds, namely isoreticular MOF–6 (IRMOF-6, Figure 2.5.6), displays rather high
methane storage capacity (155 cm 3 (STP) / cm 3 ] at 298 K and 36 atm.
Figure 2.10. Isoreticular expansion of HKUST-1. From H. Furukawa, K. E. Cordova, M. O’Keeffe
and O. M. Yaghi, Science, 2013, 341. [66] Reprinted with permission from AAAS.

16 Chapter 2
Expansion of this structures (i.e. isoreticular series of HKUST-1) could be obtained via
employing other tritopic linkers of various lengths such as TATB 3- (4,4’,4’’-(s-triazine-
2,4,6-triyl-tribenzoate) [61] and BBC 3- (4,4’,4’’-(benzene-1,3,5-triyl-tris(benzene-4,1-
diyl))tribenzoate), for example (Figure 2.10). [62] In facts, the cell volume of the largest
reported member of this series (MOF-399 ([Cu3(BBC)2]n)) is 17.4 times than that of
HKUST-1. Moreover, the isoreticular construction of MOFs to enlarge the pores is also
implemented through the expansion of the original phenylene unit of MOF-74-M [63] or
CPO-27-M (M2(dobdc), dobdc = 2,5-dioxido-1,4-benzenedicarboxylate; M = Mg, Mn, Fe,
Co, Ni, Zn, etc.). [64-65]
Synthesis of MOFs, especially reticular synthesis, has earlier mainly focused on the
preparation of new frameworks with new topologies and open structures with high
porosity which are aimed for the gas storage capacities such as hydrogen, methane and
carbon dioxide. [25, 60] Nowadays, the applications of MOFs have been more widely
explored, including some fields of physics and biology. Consequently, modification of
MOFs towards targeted applications has been more widely developed as well.
2.3.3 Way to the modification of MOFs
Beyond the traditional synthesis approaches, controlled modifications of MOFs at the
organic linkers and/or at the metal nodes, could be mainly realized in several approaches:
2.3.3.1 Direct decoration on the utilized linkers
Ligands are often decorated with various organic groups to provide guest-accessible
functional sides. [67-69] For example, Kitagawa et al. reported [Cd(4-
btapa)2(NO3)2]n∙6H2O∙2DMF (4-btapa = 1,3,5-benzene tricarboxylic acid tris[N-(4-
pyridyl)amide]) framework with amide-functionalized linker, where the highly ordered
amide groups play an important role in the interaction with the guest molecules. [68]
Moreover, the material shows selective base catalytic activity in the Knoevenagel
condensation reaction. Furthermore, introduction of the thioether side CH3SCH3CH3Schain
to the 2,5-position of 1,4-bdc and its co-assembly with Zn(II) ions lead to porous
cubic network [Zn4O(L)3], whose topology is the same as MOF-5. [69] The obtained material
exhibits a notable sensing response to nitrobenzene in the form of fluorescence
quenching. Besides, it is able to absorb HgCl2 from the ethanol solution at low

Chapter 2 17
concentrations (e.g. 84 mg/L). The pre-functionalization method is, however, somehow
limited because certain kinds of groups favor to coordinate to metal ions, which result
into frameworks with completely blocked organic sides.
2.3.3.2 Introduction of open metal sites
Open metal sites are CUS where an actual coordination number of the metal center is
lower than typically expected for its oxidation state, charge or actual ligand field. Such
CUSs can serve as binding sites for certain guest molecules (hydrogen, methane, etc.) as
well as catalytic active sites for particular reactions under Lewis acidic conditions. The
most common method to obtain CUSs is to activate (i.e. heat under vacuum) MOFs to
remove the metal-bound volatile species (e.g. water, DMF, methanol, etc.). Indeed, this is
often a case for several well-known MOFs such as HKUST-1 ([Cu3(BTC)2]n) and other
members of this family, as well as MOF-74 ([(M2(dobdc)H2O]n) (Figure 2.11). [70-71]
Figure 2.11. Representation of the crystal structure of HKUST-1 as well as the generation of Cu-
CUS at the PW units upon activation. Green, Cu atoms; red, O atoms; gray, C atoms. Hydrogen
atoms are omitted for clarity.
Apart from this conventional method, the unsaturated metal centers can be introduced by
employing similar metal chelating dicarboxylates, [72-74] 2,2’-bipyridine-5,5’-dicarboxylate

18 Chapter 2
(H2BPDC) [75] or other bridging ligands, [76] which are not part of the inorganic building
blocks of a given framework. Moreover, MOFs with open metal sites featuring diverse or
enhance property can be achieved by using other metal ions in place of those metal
precursors used in the known MOFs. By directly employing metal precursors containing
another metal-ions and the same linkers during the synthesis of MOFs, the formation of
the isostructural MOFs is expected. For example, analogs of HKUST-1 with the general
formula [M3(BTC)2]n where M =Zn, [77] Cr, [78] Ni, [79] Fe, [80] Mo, [81] and Ru [82] etc. were
reported by serveal groups after the appearance of [Cu3(BTC)2]n. [35] These analogs of
HKUST-1 behave rather different properties such as in gas sorption/selectivity. [78,
83] Similarly, by varying the metal in the infinite inorganic rod-type SBUs utilized for the
construction of MOF-74,([Zn2(dobdc)]n) [63] a series of isostructural M-MOF-74 with
various divalent metal ions like Mg, Co, Ni, Mn, Cd, Cu and Fe were described. [84-88] Other
families of the homologous structures prepared using the same principle are M-BTT (BTT
= 1,3,5-benzenetristetrazolate, M = Mn, Fe, Co, Cu, Cd), [89-92] for example.
2.3.3.3 Post-synthetic modification and beyond
Post-synthetic method (PSM), where the modification of ligands or metal containing
nodes is implemented after the formation of MOFs (Figure 2.12), offers an effective way
to overcome the potential for functional-group interference during MOF assembly.
Several research groups, in particular the group of Cohen, have investigated the
modification of amino and aldehyde groups in MOFs via the formation of new covalent
bonds (Figure 2.12 top). [93-100] Still, employing PSM, one can face the problem of the pore
volume decrease (caused by the functionalization reaction), which can lead to the
reduction of gas absorption capacity. Therefore, an optimized method called “postsynthetic
deprotection” was developed (Figure 2.12 bottom). [101] In this case, an organic
linker bearing protected or “masked” functional group is incorporated into a MOF under
standard solvothermal conditions, and the protecting group is subsequently removed by
a thermal [102-103] or light [98, 104] induced deprotection reaction to reveal the desired
functionality. One of the earliest example was presented by Kitagawa with the term of
“protection-complexation-deprotection” process. [102] During the protection step,
hydroxyl group of the 2,5-dihydroxyterephthalic acid (H2dhybdc) was protected by acetyl
group via acetylation to form the 2,5-diacetoxyterephthalic acid (H2dacobdc). In the
complexation/deprotection step, a MOF with a layered-pillared structure was obtained by

Chapter 2 19
the rection of H2dacobdc, bipyridine and Zn(II) in DMF, with the simultaneous removal of
the acetoxyl groups completely. This strategy was found to be useful for preventing
interpenetration, introducing functionality, and controlling pore diameter. [105]
Figure 2.12. A general scheme illustrating the concept of post-synthetic modification (PSM) on
organic likers or metal-containing nodes of MOFs. Top, covalent PSM; Middle, dative PSM; Bottom,
PSD. Reprinted with permission from S. M. Cohen, Chem. Rev., 2012, 112, 970-1000. [101] . Copyright
(2012) American Chemical Society.
Moreover, dative PSM (Figure 2.12 middle) involves heterogeneous chemical reactions to
functionalize preassembled MOF structures via modification of metal-containing nodes
(SBUs) [106-107] or organic linkers [108] can be reached via the formation of dative (i.e. metalligand)
bond. [101] One of the first representative studies on dative PSM was reported by
Hupp et al. [106] It was found that axially bound DMF solvent molecules in the PW SBUs
could be fully removed from the Zn(II) PW-derived MOF by heating under vacuum.
Subsequently the desolvated MOF was treated with pyridine derivatives in CH2Cl2, leading
to materials in which the axial sites left vacant on the SBUs can be bound with pyridine
derivatives. Those obtained MOF materials demonstrated dependent H2 uptake on the
pyridine species coordinated to the SBUs, indicating properties could be
modulated/optimized by dative PSM. Férey and co-workers reported amine grafting on

20 Chapter 2
Cr III CUSs of MIL-101, displaying enhanced activities in the Knoevenagel condensation of
benzaldehyde and ethyl cyanoacetate.
Beyond the above mentioned PSM approaches, numerous conceptually different postsynthesis
routes have been emerging. Intriguing building block replacement (BBR), which
involves replacement of key structural components of the MOF, opens up a very broad
strategy for the synthesis of functionalized isostructural MOFs featuring gradient
compositions and chemical properties. Solvent-assisted linker exchange (SALE), [109-113]
which is also termed as “stepwise synthesis”, [114] , “bridging linker replacement”, [114] “postsynthetic
ligand exchange”, [115] isomorphous ligand replacement, [116] , is one of the
important method to achieve this kind of modification on MOFs. Conceptually, by the
reaction of a parent MOF and a solution of a second linker, a daughter MOF retaining the
parent MOF topology can be obtained. Besides, partial substitution of the metal ions in a
given framework with other metal ions of similar size and coordination chemistry could
be accomplished by the so-called “post-synthetic metal ion exchange”, [117] (also known as
“transmetalation”, [118] “metal metathesis” [119] or “metal-ion exchange” [120-121] ). Kahr et al.
obtained a series of mixed-metal material Mg/Ni-MOF-74 with various degrees of Ni 2+
incorporation by the post-treatment of Mg-MOF-74 and Ni 2+ solution with weak acid. [122]
These materials showed increased stability and improved accessible porosity compared
with the parent Mg-MOF-74 and Ni-MOF-74.
2.3.3.4 Mixed-component co-assembly MOFs
In addition of the post-synthetic modification on MOFs, co-assembly mixed-component
(MC) MOFs which is related to the co-crystallizing of linker or metal-nodes mixtures for
the introduction of functionalization should not be overlooked. Several research groups
reported simultaneous utilizing two or more functionalized linkers during synthesis
yielding to the formation of mixed-linker MOFs (MIXMOFs) or multivariate MOFs (MTV-
MOFs). [123-128] In fact, Yaghi et al. revealed that a number of linkers with distinct functional
groups (up to eight) can be incorporated into MOF-5 within one phase (Figure 2.13). [123]
Curiously, the properties of MTV-MOFs are not just simply a linear combination of those
of the pure components. For instance, MTV-MOF-5-EHI, as a member of this series,
demonstrates strikingly better selectivity for CO2/CO in comparison with its best samelink
counterparts. Moreover, partial metal substitution can be achieved by directly
copolymerization via mixed-metal solid solutions, [126, 129-135] where more than one type of

Chapter 2 21
metal-precursors are employed to react with the organic linkers during the synthesis
(Figure 2.14). For instance, partial substitution of Cu 2+ by Ru 3+[134] and Zn 2+[133] in the PWs
of HKUST-1 were obtained by mixing the Cu-salt with the corresponding Ru-salt and Znsalt
directly during the synthesis, respectively. Orcajo et al. prepared Co-doped MOF-5 via
co-assembly of Co(NO3)2·6H2O, Zn(NO3)2·4H2O and H2bdc during the synthesis. This
obtained material exhibited enhanced adsorption capacities for H2, CO2, and CH4 at high
pressure in comparison with Co-free MOF-5.
Figure 2.13. Schematic representation of MTV-MOF-5 structures containing up to eight different
functionalities distributed in one phase. From H. Deng, C. J. Doonan, H. Furukawa, R. B. Ferreira, J.
Towne, C. B. Knobler, B. Wang and O. M. Yaghi, Science, 2010, 327, 846-850. [123] Reprinted with
permission from AAAS.

22 Chapter 2
Figure 2.14. Schematic presentation of the metal-based solid solution approach by mixing two
different metal centers during the synthesis. Inspired by Burrows. [126]
2.3.3.5 Defect-engineered MOFs
On the basis of the concept of mixed-component MOFs, a very new approach to introduce
functionalized MOFs has been reported very recently. [136] This is related to generation of
so-called “defect-engineering MOFs” (DEMOFs), where in most cases the CUSs are
modified or generated through the incorporation of additional “defect” linkers,
modulators or through post-synthetic treatment. [137] The distinction of DEMOFs mainly
related to the degree of deviation of the local structure as well as the long-ranging
ordering of a variable fraction of the linkers and metal nodes in comparison with the
parent MOF. [138-143] However, this kind of deviation barely can be observed from MC-
MOFs. Only intrinsic defect may be present in certain conditions. [144-145] Besides, another
important features of DEMOFs which should not be overlooked is the correlation and
clustering of defect sites. Goodwin et. al used a combination of measurements and
demonstrated the controlled introduction of nanoscale correlated defects within a
hafnium terephthalate MOF UiO-66. [146] In particular, Fischer et al. reported the
incorporation of pyridine-3,5-dicarboxylate (pydc) into the HKUST-1 and its Ru analog
(Ru-MOF). [138-139] Remarkably, doping pydc resulted in the formation of mCUSs in the
obtained Ru-DEMOFs, in which along with the Ru 2+ -/Ru 3+ -species typically found in the
parent Ru-MOF framework, reduced Ru δ+ -species (0 < δ < 2) were generated. Moreover,
such Ru-mCUSs appeared to be responsible for the activity of Ru-DEMOFs in the CO
sorption as well as the catalytic hydrogenation of olefins. [138] Furthermore, doping pydc
or other similar defect linker (DL) such as 5-hydroxyisophthalic acid (5-OH-ip) into
HKUST-1(Cu-MOF), the creation of mesopores in the final Cu-DEMOFs was observed
dependent on the utilized Cu-precursors and the incorporated level of DL. [139] Due to

Chapter 2 23
appealing perspectives of this method on CUSs modification/introduction, this method is
expected to receive much attention in next years. This kind of modification of MOFs are
also involved in this dissertation. Further details will come in Chapter 4 and 5.
2.3.4 Application of MOFs
What have been addressed above show rather a broad picture demonstrating that MOFs
are attractive porous materials with a huge diversity of structures, functionalities, and
facile modification. All these make MOFs very promising for a range of applications
(Figure 2.15), [147] especially in gas storage, selective adsorption and separation.
Hydrogen and methane are good candidates for on-board fuel. A tank loaded with porous
absorbent allows gas to be stored at much lower pressure in comparison with the
identical tank without an adsorbent. Due to the high porosity and well-defined structures,
MOFs has gained significant attention being a new class of adsorbents. A lot of MOFs have
been evaluated for gas storage such as hydrogen and methane, [24, 26] which provides a
safer and more economical gas storage method. For example, MOF-5 has shown a rapid
and fully-reversible H2 storage density (66 g L -1 at 77 K, 100 bar), [148] which is very close
to the value observed for liquid hydrogen (71 g L -1 at 20.4 K, 1 bar). Later, it was found
that most of the MOFs like MOF-5 demonstrate poor performance at 298 K due to rather
weak interactions between H2 and the framework. However, remarkable enhancement of
H2 adsorption enthalpy can be achieved by designing MOFs with CUSs, [65, 70, 89]
catenation/interpenetration [149] or MOFs with heavy transition metals (e.g. Pd) which can
afford spillover effect for hydrogen storage. [150] For instance, respectively designed
Mn3[(Mn4Cl)3(BTT)8]2 bearing CUSs exhibits H2 uptake of 1.49 total wt% and 12.1 g L -1 at
298 K and 90 bar, [89] what is 77% greater than that of compressed H2 under the same
conditions. Furthermore, HKUST-1 and Ni2(dobdc) have also demonstrated high total
volumetric methane uptakes at 35 bar (225 and 235 v/v, respectively). [26] Significantly,
PCN-14 (Cu2(adip) (adip 4- = 5,5’-(9,10-anthracenediyl)di-isophthalate) containing Cu-
CUSs is also one of the best reported so far MOFs for methane storage (230 v/v, 290K, 35
bar). Note, that 35 bar is the maximum pressure achievable by most inexpensive singlestage
compressors, [151] which is also a widely used standard pressure for evaluating
adsorbents for adsorbed natural gas storage. Both rigid and flexible MOFs as well as MOF
membranes can be utilized as adsorbents for selective gas adsorption on the basis of

24 Chapter 2
adsorbate-surface interactions and/or size-exclusion (molecular sieving effect), such as
selective adsorption of N2/O2,CO2/N2, CO2/H2, etc. [23, 152-156] Moreover, separation of
alkane isotherms from natural gas is also able to be achieved by suitable design of
MOFs. [22-23, 157-158]
Figure 2.15. Widespread potential applications of MOFs. Reproduced from S. Chaemchuen, N. A.
Kabir, K. Zhou and F. Verpoort, Chem. Soc. Rev., 2013, 42, 9304-9332, with permission of The Royal
Society of Chemistry. [159]
Another widely investigated direction of MOFs applications is catalysis. Size- and shapeselective
catalytic behavior could be achieved by utilizing MOFs with suitable porosity and
functional groups/sites. [68, 160] For instance, functionalized 3D MOF with amide groups,
[Cd(4-btapa)2(NO3)2]n∙6H2O∙2DMF, demonstrates catalytic selectivity in the Knoevenagel
condensation reaction due to the relationship between the size of the reactants and the
pore window of the host. [68] Significantly, the presence of catalytically active transitionmetal
centers (loaded nano-particles (NPs), grafted metal complex, or active metal sites)
as well as the organic functional sites in MOFs also enable this kind of porous materials to
be catalysts in a variety of reactions. [27-29, 161] It is typical, that CUSs in MOFs serve as
Lewis-acid catalytic sites to speed up the reactions run under Lewis-acid conditions. [161]
For example, both MIL-101([Cr3F(H2O)2O(bdc)3]) and HKUST-1(Cu3(BTC)2)n) featuring
exposed CUSs have been reported as good catalysts for cyanosilylation of aldehydes. [162-
163] Besides, Lin, Kim and Kaskel demonstrated applications of homochiral MOFs in

Chapter 2 25
asymmetric catalysis. [164-166] Very recently, the application of MOFs as biomimetic
catalysts has been reviewed as well. [167-168] Some researchers also exploit the advances of
MOFs as photocatalysis. [169-170] Apart from these two highlighted fields, applications of
MOFs are certainly studied also in magnetism (ferromagnetic, antiferromagnetic,
ferromagnetic, frustration and canting properties), [171-173] proton [174-178] and electrical [179-
181] conductivity, luminescence and sensors chemistry, [182-186] drug storage and
delivery. [187-188] Thus, in the near future breakthroughs with the continual developments
in these and new applications are expected.

3 Controlled secondary building unit approach to the
formation of the isostructural Ru II,II and Ru II,III analogs of
[M3(BTC)2]n
Abstract
Controlled secondary building unit approach (CSA) was employed to derive a series of
ruthenium metal-organic frameworks (MOFs) of the general formula [Ru3(BTC)2Yy]n·G g
(BTC = 1,3,5-benzenetricarboxylate; Y = counter-anion, G = guest molecules, 0 ≤ y ≤ 1.5),

Chapter 3 27
which are structural analogs of [M3(BTC)2]n (M = Cu, Zn, Ni, Cr, Mo). As Ru-precursors for
CSA mixed-valence [Ru2 II,III (OOCR)4X] and [Ru2 II,III (OOCCH3)4]A compounds, with various
nature of the anions X and A (strong coordinating X (like Cl - ) and weakly coordinating A
(like [BF4] - or [BPh4] - )) as well as alkyl groups at the carboxylate ligand R (R = CH3 or
C(CH3)3 ), were employed. Additionally, [Ru2 II,II (OOCR)4] complexes without any counterions
were tested as Ru-source for Ru-MOF preparation. Systematic studies were
conducted and five phase-pure Ru-MOFs were obtained. The set of characterization data
support indicated the analytical compositions and the structural analogy of the prepared
Ru-MOFs with the [M3(BTC)2]n family. The oxidation state of the Ru-sites in the obtained
solids was studied by the X-ray absorption near edge structure (XANES) spectroscopy.
The chosen Ru-precursors, optimized synthetic and activation protocols allowed
improvement of the overall crystallinity, purity (in terms of residual solvent molecules)
and porosity of the Ru-MOF materials.

28 Chapter 3
3.1 Preparation and investigation of the Ru II,III -analogs of [M3(BTC)2]n *
3.1.1 The family of [M3(BTC)2]n
Figure 3.1. 3D crystal structure of [Cu 3 (BTC) 2 ] n (Cu-HKUST-1) viewed along the (100) direction.
Green, red and gray balls stand for Cu, O and C atoms, respectively. Hydrogen atoms are omitted
for clarity.
[Cu3(BTC)2]n (also known as HKUST-1 [35] or MOF-199 [36] , BTC = 1,3,5-
benzenetricarboxylate), first reported by Chui et al. in 1999, represents one of the most
well investigated MOFs synthesized at the early stages of MOF chemistry. The 3D
structure of [Cu3(BTC)2]n, with the space group Fm-3m, features paddlewheel (PW)
dicopper(II) tetracarboxylate building blocks where Cu II -ions adopt pseudo-octahedral
coordination geometry with the axial sites occupied by H2O (Figure 3.1). These
coordinated water molecules H2O can be easily removed by heating the samples under
vacuum (i.e., activation) leading to exposed Cu II -ions, which subsequently could serve as
active Lewis acid sites in catalytic reactions (Figure 3.2). [189-190] Moreover, the interaction
* The main results of this part are covered in the following publication: W. Zhang, O. Kozachuk, R. A. Fischer,
et al. Eur. J. Inorg. Chem. 2015, 3913–3920.

Chapter 3 29
between gas molecules and such coordinatively unsaturated sites (CUS) center often
enhance the general adsorption properties of the MOF materials. [191-192]
Figure 3.2. Modification of the Cu-sites in Cu-HKUST-1 after activation (and i.e., formation of Cu-
CUS) and substrate coordination. Green, red, gray and violet balls represent Cu, O, C atoms and
substrate (either gas or liquid molecules), respectively.
Given the presence of metal CUSs and the permanent porosity, a number of isostructural
[M3(BTC)2]n frameworks with various 3d and 4d metal-ions (M = Mo, [81, 83] Cr, [78, 83] Fe, [80]
Ni, [79, 83] Ru [82, 138] and Zn [77] ) were reported later. Among them, [Cr3(BTC)2]n featuring Cr II
open metal sites exhibited reversible and highly-selective binding of O2. More
interestingly, among this formally homologous series as suggested by the (simplified)
general formula [M3(BTC)2]n, the Fe and Ru analogs (abbreviated hereafter as Fe-MOF and
Ru-MOF) were found to possess mixed-valence M II,III PW units, which might be of great
use due to their potential photo and redox properties. [193] However, Fe-MOF was reported
with no measurable porosity while Ru-MOF presented quite high porosity as well as good
thermal and chemical stability. In fact, as a consequence of the mixed-valence state, the
actual chemical composition and microstructure of these (Fe, Ru)-MOFs turned out to be
more sophisticated. Counter-ions (X) and strongly bound guest molecules (G) seem to be
notoriously present even after activation. The incorporation of these components as a
function of synthetic conditions must be taken into account. Thus, the empirical formula
of these materials should be more precisely written as [M3(BTC)2Yy]n·G g.
3.1.2 Background and the state-of-the-art in research on Ru-analogs of
[M3(BTC)2]n
Looking through all the reports, the parent material [Cu3(BTC)2]n (HKUST-1) can be
obtained through solvothermal, [35] electrochemical [194] , microwave syntheses [195] and
others [196-197] . However, the synthesis of the Ru-analog is far less investigated. [82, 193] The

30 Chapter 3
formula of [Ru3 II,III (BTC)2Cl1.5]n was initially assigned and obtained either from RuCl3 or
[Ru2(OOCCH3)4Cl]n. The powder X-ray diffraction (PXRD) data support an analogous
structure as [Cu3 II,II (BTC)2]n. Element-analytical, magnetic, X-ray photoelectron
spectroscopy (XPS) and probe molecule adsorption combined with IR spectroscopy
pointed to a mixed-valence Ru2 II,III PW units as the framework’s nodes. The Cl - counterions
are most likely strongly coordinated to the Ru-centers to balance the overall charge
of the framework. This material shows both good chemical and thermal stability;
however, the Ru-centers are partly occupied and coordinated Cl cannot be removed by
standard activation protocols. Hence, the number of active sites for catalysis and gas
sorption is obviously reduced. Later, another analog described as [Ru3(BTC)2][BTC]0.5 was
reported by Dincă et al. [83] The authors employed [Ru2(OOCC(CH3)3)4(H2O)Cl] as
ruthenium source. The absence of Cl - in the samples of [Ru3(BTC)2][BTC]0.5 was postulated
based on elemental analysis data only, and extra framework BTC serving as counter-ion
was suggested. This solid showed better Brunauer-Emmett-Teller (BET) surface area
values compared to the [Ru3 II,III (BTC)2Y1.5]n prepared first in our group. However, the
presence of guest molecules such as trimethyl-acetate or acetate (arising from CSA and/or
synthetic conditions) in the structure still could not be unambiguously determined or
ruled out. Thus, modification of the starting Ru-sources used for the synthesis seems to
be interesting for tuning the metal sites (i.e., oxidation state and CUS), composition and
stability of the HKUST-1 analogous Ru-MOFs, which in turn can have a profound impact
on other properties such as porosity and catalysis, for instance.
Previously [Ru3 II,III (BTC)2Y1.5]n has been studied where the mixed-valence Ru II,III state was
characterized in particular by CO and CO2 adsorption monitored by the FT-IR
spectroscopy at low temperature under ultra high vacuum (UHV) conditions. [198] Also, the
co-assembly of BTC with pyridine-3,5-dicarboxylate (pydc) to yield mixed-component
(linker-based) solid solution type samples of the formula [Ru3(BTC)2-x(pydc)xYy]n·G g was
achieved. These so-called “defect engineered” Ru-MOFs showed interesting new
properties (e.g. dissociative chemisorption of CO2). [138] Motivated by these promising
results, it would be of great interest to investigate the synthesis of the parent Ru-MOF in
more systematic fashion, dependence on Ru-precursors featured with diruthenium PW
units (e.g. applying CSA), variation of the reaction conditions, work-up and activation in
order to optimize the sample quality.

Chapter 3 31
In this Chapter CSA is employed to systematically study the factors of synthetic conditions
affecting the overall structure, composition and properties (in particular, thermal
stability, porosity, etc.) of the Ru-based HKUST-1 analogous compounds (Scheme 7.3).
Various Ru precursors, namely [Ru2(OOCR)4X] and [Ru2(OOCCH3)4]A, in which R = CH3 or
C(CH3)3; X = Cl; A = BF4 or BPh4, were adopted as starting materials in order to modify the
properties of the obtained Ru-MOF samples while maintaining the isoreticular
relationship to HKUST-1. Switching from the -CH3 to bulkier R-group (e.g. -C(CH3)3)
should increase the solubility of the polymeric ruthenium precursors, and, subsequently,
would influence the kinetics of the MOF synthesis (better/faster nucleation and growth).
On the other hand, employing weakly coordinating anions (WCA), like [BF4] - or [BPh4] - ,
may allow modulation of the CUS within the Ru-MOF. Utilizing these counter-ions, A
avoids the formation of a polymeric (insoluble) structure of the Ru precursors on one
hand. On the other hand, it is anticipated that A being less prone to be incorporated into
the framework via coordination to the Ru II,III -centers and, thus, may be removed by
washing and activation of the samples. Unless, note, that H2O is always around in the
solvothermal reactions and formation of -OH and its incorporation as component X must
be also considered even in case of using WCA A, such as BF4 or BPh4.
3.1.3 [Ru3(BTC)2Yy]n·G g obtained by CSA using [Ru2(OOCR)4X] and
[Ru2(OOCCH3)4]A: synthesis and characterization
3.1.3.1 CSA-precursors
The Ru-precursors ([Ru2(OOCR)4X] and [Ru2(OOCR)4]A were prepared according to the
literature (Scheme 7.1). [199-202] Characterization of all precursors confirmed the
compositions and structures being expectedly analogous to the reported compounds. All
structures consist of Ru2-clusters coordinated by four carboxylic groups. Thus, this kind
of binuclear units (PWs) are similar to the building units in the [Cu3(BTC)2]n framework,
affording the idea to construct the isostructural [Ru3(BTC)2]n by means of the CSA. The
PXRD patterns of [Ru2(OOCCH3)4Cl] (SBU-a, R = CH3) showed the phase-purity of the
compound (Figure 7.3). [203] Furthermore, following the well documented literature
method, single crystals of [Ru2(OOCC(CH3)3)4(H2O)Cl](CH3OH) (SBU-b, R = C(CH3)3) were
obtained. The cell parameters and other crystal structure data of SBU-b are presented in
Table 7.1 and Figure 7.5. To note, the obtained crystallographic data are of superior

Intensity, a. u.
32 Chapter 3
quality as compared to the literature reference. Complementary characterizations such as
1 H-NMR and PXRD reveal also high purity of SBU-b (Figures 7.6 and 7.7). In addition,
[Ru2(OOCCH3)4(THF)2](BF4) (SBU-c) were obtained as the microcrystalline powder and
was fully characterized (Figure 7.8). The synthesis of [Ru2(OOCCH3)4(H2O)2](BPh4) (SBUd)
reported in the literature lead to the immediate decomposition of the product after
filtration. [204] However, when we employed [Ru2(OOCCH3)4(H2O)2]2(SO4) instead of
[Ru2(OOCCH3)4Cl] [199] as Ru-precursor, our target [Ru2(OOCCH3)4(H2O)2](BPh4) was
successfully obtained (Figure 7.9).
3.1.3.2 Synthesis, activation and thermal properties of Ru-MOF 1-4
4
3
2
1
Cu-BTC_sim
10 20 30 40 50
2, degree
Figure 3.3. PXRD patterns of the as-synthesized samples 1-4 as well as the simulated PXRD
patterns of the reported [Cu 3 (BTC) 2 ](Cu-BTC_sim).

Chapter 3 33
All Ru-MOFs 1-4 of the general formula [Ru3(BTC)2Yy]n·G g (Y = Cl, F, OH…; G = H2O,
CH3COOH, (CH3)3CCOOH, H3BTC,…; 0 ≤ y ≤ 1.5) were obtained employing [Ru2(OOCR)4X]
or [Ru2(OOCCH3)4]A precursors under solvothermal conditions in a similar way as we
reported earlier. [82] The subsequent activation (i.e., removing of the incorporated
solvent/guest molecules) was conducted at 150 °C for 24 h under dynamic vacuum (ca.
10 -3 mbar). As revealed by the PXRD patterns (Figure 3.3), the prepared Ru-MOFs 1-4 are
phase-pure crystalline solids that are isostructural to [Cu3(BTC)2]n. Ru-MOFs 2 and 4
showed better crystallinity compared to the samples 1 and 3. The coordination of the
carboxylic groups of framework BTC in the activated Ru-MOF samples is indicated by the
strong-intensity bands at 1429 cm -1 and 1359 cm -1 in the FT-IR spectra (Figure 3.4).
Notably, the Ru-MOFs obtained from [Ru2(OOCCH3)4]A, in which Y = [BF4] - and [BPh4] - ,
show similar IR spectra with the other two samples. In other words, the incorporation of
[BF4] - counter-ion in the structure of 3 can be ruled out, as no characteristic ν(B-F) band
was observed at 1073 cm -1 . It is not possible to unambiguously determine the presence of
[BPh4] - based only on the IR spectra because of the overlapping vibrations of [BPh4] - and
BTC. Further analytical evidences in this respect will be discussed later.
Figure 3.4. IR spectra of the activated Ru-MOFs 1-4.

34 Chapter 3
After activating the Ru-MOFs, thermal gravimetric analysis (TGA) was performed
demonstrating stability of the samples 1-4 up to 200 °C. Interestingly, Ru-MOF 4 is the
most stable among the samples of discussed series and can be heated up to 250 °C without
decomposition (Figure 3.5). Both as-synthesized and activated phases of the sample 1
showed weight loss around 100 °C, which can be attributed to either a) loss of the residual
coordinated solvent within the framework or b) adsorbed molecules such as water during
transfer of the activated sample from the glovebox to the instrument. Ru-MOF 2 shows a
slow weight decrease at low temperature range (30-150 °C), which is similar to the
sample 1. Noteworthy, no similar observation was found in the curves of 3 and 4, meaning
there are less residual solvent molecules trapped as compared to the other two samples
1 and 2. Thus, it suggests that the pores of the frameworks 3 and 4 are more accessible
and activation (desorption of the guest molecules) is facilitated.
Figure 3.5. TG curves of the activated Ru-MOFs 1-4.

Intensity, a. u.
Chapter 3 35
3.1.3.3 Acid digestion and composition of the obtained Ru-MOFs 1-4
4_ex
4
3_ex
H(BTC)
H(BPh 4
)
H(AcO)
3
2_ex
H(PivO)
2
1_ex
1
10 8 6 4 2 0
, ppm
Figure 3.6. NMR spectra (measured in DCl/DMSO-d 6 ) of the Ru-MOF samples before (1-4) and
after solvent exchange (1-4_ex) . All spectra were normalized by dividing the intensity of H(BTC),
respectively. PivO = pivalate, AcO = acetate. Due to the sensitivity of water peak to the solution
conditions, the proton resonance of H 3 O + varies here in the range of 4-6 ppm, dependent on the
concentration of DCl in the total solution.
To get more insight into the microstructures (i.e. analytical purity) and composition of the
materials 1-4, 1 H-NMR analysis of the acid-digested (in DMSO-d6/DCl mixture) Ru-MOF
samples was performed. Thus, the 1 H-NMR spectra revealed, that besides the signals at δ
= 8.61 ppm attributed to the aromatic protons of BTC, one additional resonance at δ = 1.88
ppm is seen and can be assigned to the protons of the residual acetic acid (AcOH) for all
four Ru-MOFs samples (Figure 3.6). For Ru-MOF 2, the spectrum shows also an additional
signal at δ = 1.05 ppm, which corresponds to the protons of the residual pivalic acid
(PivOH) (Figure 3.7). The spectra suggest that the larger R-group (-C(CH3)3 instead of -
CH3) in the Ru-SBU leads to more impurity in the synthesis of MOFs in addition to the

36 Chapter 3
presence of the residual acetic acid in Ru-MOF 1, 3 and 4. Note, acetic acid has been a
major component of the solvent medium during the synthesis. In the NMR spectrum of the
sample 4 (Figure 7.11), signals assigned to trace amount of [BPh4] - were detected. This
residue can be removed completely after washing and solvent exchange (for further
explanation see the next section). The integrations of these signals for each Ru-MOF are
listed in Table 3.1. In summary, Ru-MOF 3 and 4 contain lower amounts of the residual
acetic acid. This again brings to the conclusion that these two samples are analytically
purer as compared to the 1 and 2. Moreover, samples of 3 and 4 could be more
quantitatively digested by the employed protocol in the same amount of solvent
DCl/DMSO-d6 mixture, providing, therefore, more intense signals in the NMR spectra for
each Ru-MOF sample.
SBU-b
2
H(BTC)
H(AcO) H(PivO)
10 8 6 4 2 0
, ppm
Figure 3.7. Acid-digested (DCl) 1 H-NMR spectra of SBU-b (top) and 2 (bottom) (solvent: DMSOd
6 ). The tiny peaks at around 0.8 and 1.2 ppm are due to H-grease.

Chapter 3 37
Table 3.1. Comparison of the integrals of the 1 H NMR signals in the samples 1-4 (before solvent
exchange) in comparison with 1-4_ex (after solvent exchange) to determine the linker to guest
molecular ratios (BTC = 1, 3, 5-benzentricarboxylate, AcO = acetate, PivO= pivalate).
Ru-MOFs H(BTC) : H(AcO) H(BTC) : H(PivO)
1 1 : 2.4 -----
1_ex 1 : 0.8 -----
2 1 : 1.5 1 : 1.5
2_ex 1 : 1.2 1 : 0.8
3 1 : 1.6 -----
3_ex 1 : 0.9 -----
4 1 : 0.7 -----
4_ex 1 : 0.7 -----
3.1.4 Pre-activation by solvent exchange
The presence of high amounts of acetic acid and pivalic acid arising from both, the Ru
precursor and the reaction solvent mixture (which contains excess of acetic acid)
apparently leads to partly pore-filling with the residual solvent (acid), which
consequently may considerably affect or restrict the Ru-MOF properties. As revealed,
these components cannot be removed completely regardless of the applied activation
procedure (i.e. 150 °C for 24 h under dynamic vacuum (ca. 10 -3 )). Our attempts to slightly
modify the reaction conditions, namely by reducing the quantity of acetic acid and/or
using acetic acid free conditions yielded either amorphous products and/or prevented the
substitution of RCCOOH in Ru-SBUs, affording just non-reacted starting materials (Figure
7.12). Noteworthy, the reactants concentration in synthesis of the Ru-MOF 1 is quite
crucial and attempting to vary the amounts of solvent with the same molar ratio of Ruprecursor
and H3BTC was not so successful to get crystalline materials. Therefore, we
conducted additional experimental studies directed to improve the activation procedure
(i.e., minimize the amount of the strongly retained guest molecules) and, thus, improve
the sample quality and access to the pores and open metal sites. For this reason we
introduced an additional step to the activation procedure earlier mentioned. [138] Namely,

Intensity, a. u.
38 Chapter 3
the as-synthesized Ru-MOF samples were soaked in a large amount of (coordinatively)
more inert solvent (water or ethanol, 80-100 ml) and stirred (for an average of 4 h) in
order to wash out or replace strongly coordinated/adsorbed acetic or pivalic acid.
Subsequently, the solvent was replaced by fresh portion and the samples were left
standing overnight. This “solvent exchange” was repeated for each sample three times.
Afterwards the samples were collected and dried under ambient conditions. The washed
and dried samples (1-4_ex) were then “typically” treated again according to the
established activation procedure for Ru-MOF: heating at 150 °C for 24 h under dynamic
vacuum (ca. 10 -3 bar) in order to finally remove all adsorbed solvent and residual guests.
3.1.5 Study of [Ru3(BTC)2Yy]n·G g after solvent exchange
3.1.5.1 Phase purity and stability
4-ex
3-ex
2-ex
1-ex
Cu-BTC_sim
10 20 30 40 50
2, degree
Figure 3.8. PXRD patterns of the Ru-MOF samples after solvent exchange (1-4_ex) in comparison
with the simulated patterns of Cu-HKUST-1 (Cu-BTC_sim).

Chapter 3 39
Figure 3.9. IR spectra of the activated Ru-MOFs before (1-4) and after “solvent exchange” (1-
4_ex).
The PXRD patterns of the samples 1-4_ex match well with those of the [Cu3(BTC)2]n,
suggesting fully preserved structural integrity of the Ru-frameworks after employed
solvent exchange procedure (Figure 3.8). The IR spectra of the 1-4_ex further substantiate
that the structure of the Ru-MOFs is retained (Figure 3.9). Both reveal the chemical
stability of the 1-4 after solvent exchange. As expected, the amount of residual guest
molecules (in this case, acetic acid, etc.) hosted by the frameworks of 1, 2 and 3 decreases
considerably after applying an additional “solvent exchange”, which is clearly indicated
by the comparison of the 1 H-NMR data of the digested and activated Ru-MOFs samples
before (1-3) and after solvent exchange (1-3_ex) (Table 3.1 and Figure 3.6). In fact, the
integration of the signals attributed to AcOH (δ = 1.88-1.93 ppm) in 1_ex and 1
corresponds to 0.8:1 vs. 2.4:1. Notably, pivalic acid in 2 was removed even to a greater

40 Chapter 3
extent than acetic acid (Table 3.1). At the same time, application of solvent exchange to
Ru-MOF 4, containing the lowest amount of the guest molecules, does not have significant
effect. The integration of the signals due to acetate protons reveals the same values,
suggesting the amount of the acetate before and after exchanging is constant. Comparing
all 1-4_ex samples, Ru-MOF 4 is the most promising one, with the lowest amount of guest
molecules G. In addition, the tiny amount of residual [BPh4] - in 4 was removed after
solvent exchange (Figure 3.6), as confirmed by the absence of the corresponding proton
signals at 7.3 ppm.
Figure 3.10. TG curves of the Ru-MOFs obtained from various Ru-SBUs before (1-4) and after (1-
4_ex) solvent exchange procedure.
From the TGA 1-4_ex samples (Figure 3.10) it is evident that these materials still possess
good thermal stability after utilized solvent exchange and do not decompose until 200 °C.
The shape of the TG curves of the 1_ex and 3_ex does not change after solvent exchange
and suggest a decomposition temperature of 200 °C and 250 °C, respectively (Figure 3.10).
In contrast, of the thermal stability of Ru-MOF 2 substantially decreases after solvent

Chapter 3 41
exchange. This might stem from the presence of at least two different guest molecules
(acetic acid and pivalic acid), meaning there are more molecules which sustain the whole
framework in some extent through (weak) coordination compared to 1 and 3. Hence, the
stability considerably decreases after solvent exchange while maintaining the structure
(Figure 3.10). The same behavior is observed for Ru-MOF sample 4, most likely due to the
removal of [BPh4] - counter-ions, which previously stabilized the framework (Figure 3.10).
3.1.5.2 Composition determination
To quantitatively determine the composition of Ru-MOFs 1-4_ex elemental analysis (EA)
and Energy-dispersive X-ray spectroscopy (EDX) were subsequently performed. From
our earlier reports, [82, 138] EA results indicated the molar ratio of Ru : Cl being 3 : 1.5. The
XPS studies showed two different Ru-species (Ru III and Ru II ) as well as the presence of
chlorine, suggesting Cl - being the major couter-ion to balance the charge of the
framework. [82] As revealed in the present studies, the molar ratio of Ru : Cl in 1_ex slightly
differs from the sample before solvent exchange (Ru : Cl = 3 : 1.5) [138] and equals to ~ 3 :
1 (Table 3.2). The presence of chlorine was additionally confirmed by the EDX elemental
mapping of Ru and Cl (Figure 3.11). It should be noted, that the analytically determined
Ru-content (weight percentage by AAS) in the exchanged materials (1_ex) decreased from
36.29 % to 30.45 %. [82, 138] Nevertheless, all characterizations proved preservation of
crystallinity, porosity as well as thermal stability (by TGA). Based on these observations,
together with the preserved BET surface area (SBET) observed after solvent exchange (see
the details for next section on porosity), creation of the internal “structural defects” (i.e.
missing of Ru-nodes) in the solvent exchanged sample 1_ex could be expected. As
mentioned earlier, acetic acid is present in the discussed Ru-MOFs. The residual acetic
acid (or acetate) could be included into frameworks mainly in three ways: i) it can be
deprotonated and act as the counter-ion (coordinated to the Ru-center or sitting around
the PW units) to compensate the charge of the [Ru2] 5+ units (Figure 3.12a); ii) inherent
structural defects due to the incomplete substitution by the BTC within used Ru-SBUs
(Figure 3.12b and c); iii) the acetic acid molecules (without deprotonation) might be
accommodated within the pores of the frameworks. Activation procedure of the assynthesized
samples could hardly direct remove the residue of the acetic acid in the
framework. Nonetheless, application of additional solvent exchange method results in
partly elimination of the residual acetic acid, and might consequently create the missing

42 Chapter 3
Ru-nodes. Therefore, relatively reduced Ru-content is observed in the sample 1_ex. This
kind of observation is mostly likely related to two possibilities: i) the strong stirring
during the washing procedure; ii) slower substitution kinetics on the acetate coordinated
Ru2 II,III -PW centers in comparison with Cu2-PW centers (rapid substitution kineties).
Table 3.2. The obtained elemental analysis data and the calculated formula of 1-4_ex after solvent
exchange. BTC = 1,3,5-benzenetricarboxylate, H 3 BTC = 1,3,5-benzenetricarboxylic acid, AcO =
acetate, AcOH = acetic acid, PivOH =pivalic acid.
Samples and Formula wt% C wt% H wt% Cl wt% F wt% Ru
1_ex
[Ru 3 (BTC) 2 Cl(AcO) 0.5 ] n·(AcOH) 1.5 (
H 3 BTC) 0.1 (H 2 O) 4
2-ex
[Ru 3 (BTC) 2 Cl 1.2 (OH) 0.3 ] n·(H 3 BTC)
0.15(AcOH) 2.4 (PivOH) 0.45
3_ex
[Ru 3 (BTC) 2 F 0.7 (OH) 0.8 ] n·(AcOH) 2.4
(H 3 BTC) 0.5 (H 2 O) 3
4_ex
[Ru 3 (BTC) 2 (OH) 1.5 ] n·(H 3 BTC) 0.8 (A
cOH) 1.4 (H 2 O) 3
Found 27.26 1.65 3.41 - 30.45
Cal. 28.5 2.31 3.67 - 31.40
Found 31.57 2.11 4.16 - 29.27
Cal. 32.14 2.18 4.31 - 30.73
Found 29.28 1.28 - 1.09 24.18
Cal. 31.30 2.44 - 1.27 29.90
Found 32.15 1.60 - - 26.64
Cal. 32.05 2.30 - - 28.90
Figure 3.11. SEM image and the EDX elemental Ru- and Cl-map of the 1_ex sample.

Chapter 3 43
Figure 3.12. Possible coordination of the acetic acid in the obtained Ru-BTC structures.
In case of Ru-MOF 2, EDX elemental mapping images (Figure 3.13) also indicate the
presence of chlorine. Besides, EA results indicated the Ru : Cl molar ratio to be ~ 3 : 1.2,
suggesting Cl - serving here also as a major counter-ion to balance the charge of the [Ru2] 5+
PW units, in analogy to 1. The EDX, EA results combined with the 1 H-NMR data of 2_ex
match well with a formula [Ru3(BTC)2Cl1.2(OH)0.3]n·(H3BTC)0.15(AcOH)2.4·(PivOH)0.45,
which includes a small amount of unreacted H3BTC, possibly residing in the pores rather
than being deprotonated (as counter-ions). Although Ru-MOF 2_ex features higher
crystallinity than other Ru-MOFs obtained from various Ru-SBUs, changing the R groups
to -C(CH3)3 in the starting ruthenium precursor makes the whole system more
complicated by introducing a new kind of impurity (pivalic acid) with respect to the
analytical purity.
Figure 3.13. SEM image and the EDX elemental maps for Ru and Cl of the 2_ex sample.
In case of sample 3, the Ru : F molar ratio calculated from the EA data of the 3_ex is ~3 :
0.7, suggesting the presence of strongly coordinated F - counter-ions. However, as the F-
amount is rather low, the distribution of F could not be mapped via EDX (Figure 3.14).
Still, this agrees with the absence of BF4 (monitored by IR) and can be explained by in situ

44 Chapter 3
decomposition of [BF4] - into F - and BF3 during the MOF synthesis. As expected, lower
amounts of counter-ions were observed compared to 1 and 2, when adopting WCAs as
counter-ions in the starting Ru-SBU. Although, there are guest molecules in the material,
the characterization of the Ru-solids after applied solvent exchange procedure indicates
a better purity control (i.e. decrease of the types and amounts of guest molecules) than in
case of 2.
Figure 3.14. SEM image and the EDX elemental maps for Ru and F of the 3_ex sample.
Based on the EA and NMR analyses as well as the assumption of the presence of [OH] - to
help the charge balance, the empirical formula of Ru-MOF 4_ex matches well with
[Ru3(BTC)2(OH)1.5]n·(H3BTC)0.8(AcOH)1.4(H2O)3. In this case our data support the
conclusion that the strongly coordinating counter-ion Y of the final mixed-valence Ru-
MOF may not stem from the employed Ru-SBU.
3.1.5.3 Porosity comparison
In order to compare the porosity of HKUST-1 and its Ru-analogs more reasonably due to
the difference on the metal centers, SBET were calculated in the unit of m 2 /mmol according
to the values in m 2 /g unit and the corresponding molecular weight(Mw) of the samples. In
comparison with the experimental SBET value of HKUST-1 (1049 m 2 /mmol), the overall
SBET of the activated Ru-MOF solids, especially, sample 1_ex and 4_ex is measured as 964
and 941 m 2 /mmol, respectively, which suggest the good porosity of these two Ru-MOFs
(Table 3.3 and Figure 3.15). In other words, the porosity of the Ru-MOFs is not affected
after “solvent exchange”. As was indicated by the NMR studies mentioned earlier,
adopting SBU-b as the Ru-precursor revealed a decreased amount of residual AcOH in the
final framework. However, at the same time another kind of residue was introduced and
the total amount of guest molecules do not decrease much after applying the solvent
exchange procedure. Consequently, the BET surface area of the 2_ex amounts 718

Chapter 3 45
m 2 /mmol (based on the N2 isotherm) and does not differ much in contrast to the sample
before “solvent exchange” (i.e. sample 2). Notably, the thermal stability of 2_ex also
slightly decreased after solvent exchange like SBET. Hence, the overall quality of this Ru-
MOF analog is less convincing under the circumstances of this study. Interestingly, in case
of 3_ex, however, an increase of the SBET has been observed from the N2 sorption
isotherms (850 vs. 683 m 2 /mmol) (Table 3.3). The same increase of SBET has also been
observed for the sample 4_ex (941 m 2 /mmol) in comparison with the value before (916
m 2 /mmol), where the residual [BPh4] - has been removed via solvent exchange procedure
although the amount of acetic acid does not differ. Thus, in particular for Ru-MOFs 1 and
3, solvent exchange procedure proved to be a good method to reduce the amount of
residual acid molecules. In both cases the thermal stability, crystallinity and porosity were
preserved. For the material 4, solvent exchange is helpful to wash out the residual [BPh4] -
counter anions to give access to the metal-sites, while keeping the thermal stability and
porosity.
Table 3.3. Comparison of the BET surface area (S BET ) of the Ru-MOFs before (1-4) and after
solvent exchange (1-4_ex) in the unit of m 2 /g and m 2 /mmol. S BET in the unit of m 2 /mmol is
calculated by S BET (m 2 /g) and the corresponding molecular weight (M w ) determined from both EA
and 1 H NMR results. M w of 1-4_ex is obtained from the formula given in Table 3.2. The M w of
sample 1-4 is derived from the difference of the guest molecules between the samples before and
after solvent exchange, namely: M w (1) = M w (1_ex + 3.2 AcOH); M w (2) = M w (2_ex + 0.6 AcOH +
0.2 PivOH); M w (3) = M w (3_ex + 1.4 AcOH); M w (4) = M w (4_ex + 0.13 BPh 4 ).
samples S BET (m 2 /g) S BET (m 2 /mmol)
1 958 1108
1_ex 998 964
2 851 888
2_ex 728 718
3 604 683
3_ex 812 850
4 840 916
4_ex 897 941
[Cu 3 (BTC) 2 ] n
* theoretical accessible surface area.
1734 [83]
2153* [205]
1049
1301

deriv. normalized E)
46 Chapter 3
Figure 3.15. N 2 adsorption (solid symbols) and desorption (open symbols) isotherms (recorded
at 77 K) of the Ru-MOFs obtained from different SBUs. 1-4: before solvent exchange; 1-4_ex: after
solvent exchange. Squares: 1 and 1_ex; triangles: 2 and 2_ex; diamonds: 3 and 3_ex; circles: 4 and
4_ex.
3.1.5.4 Oxidation state study
SBU-a
RuCl 3
SBU-b
SBU-c
Ru
SBU-d
RuO 2
22100 22120 22140 22160
energy, eV
Figure 3.16. XANES spectra (derivative normalized absorption vs. energy) of the Ru-SBUs in
comparison with Ru-standard samples (Ru, RuCl 3 and RuO 2 ).

deriv. normalized E)
Chapter 3 47
In order to gather information on the valence of the Ru-sites in the Ru-MOFs, comparative
X-ray absorption spectroscopy (XAS) measurements were subsequently carried out. The
derivative of the edge-jump energy positions of Ru (22117 eV) and RuO2 (22131 eV) can
be used as standards, representing the oxidation states +0 and +4, respectively. On the
other hand, according to the literature, the oxidation state of Ru-center in SBU-a reveals
+2.5. [203] Hence, the same position of derived edge-jump energy (ca. 22124 eV) for SBU-a
- -d clearly indicates the oxidation state of Ru-centre to be +2.5 (Figure 3.16). To note, Ru-
MOF sample 1_ex with the edge jump position at 22126 eV matches well with its mixed
oxidation state documented in the literature by UHV-IR technique with CO probe. [82] All
the other Ru-MOFs samples (2-4_ex) exhibit their edge-jump at the range of 22123-22128
eV, suggesting the mixed oxidation state of the Ru-centers in their structure as well
(Figure 3.17). The study on deviation of local coordination environments within these Ru-
MOFs due to the change of the counter-ions (in particular by Extended X-Ray Absorption
Fine Structure (EXAFS)) is one of our further direction.
Ru
Ru NP
3_ex
4_ex
RuO 2
2_ex
1_ex
22100 22120 22140 22160
energy, eV
Figure 3.17. XANES spectra (derivative normalized absorption vs. energy) of Ru-MOFs obtained
from various Ru-SBUs (1-4_ex) in comparison with Ru-standard samples (Ru, Ru NP and RuO 2 ).

48 Chapter 3
3.1.6 Summary
Applying CSA, a series of Ru-MOFs [Ru3(BTC)2Yy]n·G g were synthesized under
solvothermal conditions and fully characterized(Table 3.4). Varying the R-group and
nature of the counter-ion in the Ru-SBU ([Ru2(OOCR)4X] and [Ru2(OOCCH3)4]A), tuning
(up to a certain extent) the local environment of the metal sites while retaining the same
structure were achieved. Changing the R-group at the carboxylate in the Ru-SBU from -
CH3 to bulkier –Rs, for example -C(CH3)3, leads to a striking improvement of the
crystallinity of the final MOFs. However, considering the MOF compositions, the whole
picture gets complicated, as residual guest molecules/species G could stem from both
different R-groups in the Ru-SBU ([Ru2(OOCR)4X]) and solvents (including used
carboxylic acids).
Table 3.4. Summary of the preparation, composition and S BET in [Ru 3 (BTC) 2 Y y ] n·G g (1-4_ex). BTC
= 1,3,5-benzenetricarboxylate, H 3 BTC = 1,3,5-benzenetricarboxylic acid, AcO = acetate, AcOH =
acetic acid, PivOH =pivalic acid.
sample
employed SBUs for synthesis
Counter-ions
Y
guest
molecule G
S BET
(m 2 /mmol)
1_ex
SBU-a
[Ru 2 (OOCCH 3 ) 4 Cl] n
Cl, AcO
1.5AcOH,
0.1H 3 BTC,
4H 2 O
963
2_ex
SBU-b
[Ru 2 (OOCC(CH 3 ) 3 ) 4 (H 2 O)Cl](CH 3 OH)
Cl, OH
2.4AcOH,
0.15H 3 BTC,
0.45PivOH
718
3_ex
SBU-c
[Ru 2 (OOCCH 3 ) 4 (THF) 2 ](BF 4 )
F, OH
2.4AcOH,
0.5H 3 BTC,
3H 2 O
850
4_ex
SBU-d
[Ru 2 (OOCCH 3 ) 4 (H 2 O) 2 ](BPh 4 )
OH
1.4AcOH,
0.8H 3 BTC,
3H 2 O
941
Besides this, the counter-ion Cl - is still present to compensate the charge of the [Ru2] 5+ PW
units. Therefore, keeping the same R-group (-CH3) in the Ru-SBU, the Cl - counter-ions
were replaced by WCAs. As expected, the ruthenium centers were modified through
introducing more weakly coordinating anions. The more coordinatively active the
counter-ions in the Ru-SBU are, the easier they coordinate to the metal centers in the final
MOF structure. In spite of the fact, that BF4 was absent in the structure of 3_ex, F - was
found in the material by EDX and EA. Therefore, Ru-SBUs with more stable WCA, like BPh4,

Chapter 3 49
were investigated as well. Remarkably, by introducing [BPh4] - to the Ru-SBUs, MOF
materials that do not include BPh4 were successfully obtained. Interestingly, the amount
of residual included guest molecules G in the modified MOFs (3_ex and 4_ex) decreases
compared to respective Ru-MOFs obtained starting from [Ru2(OOCR)4Cl]. In particular,
sample 4_ex which contains the lowest amount of the guest molecules (acetic acid), is the
first material obtained in the series of Ru-analogs of [Cu3(BTC)2]n that includes no strongly
coordinating counter-ions X originating from the used Ru-SBUs.
Solvent exchange procedure was introduced to achieve better removal of the guest
molecules without damaging the framework integrity after activation. As expected, after
applying such improved activation procedure, the counter-ions [BPh4] - and most of the
guest and solvent molecules (like acetic acid) were washed out of the material while the
crystallinity and thermal stability are retained. These studies are particularly crucial for
the future investigation and elaboration of these materials for targeted applications, such
as in selective sorption and catalysis. In summary, the synthesis of the Ru-MOF is still
difficult to optimize further. Nevertheless, the investigations herein afford better
understanding and directions towards not only HKUST-1 analogs but also other MOFs
with PW SBU.

50 Chapter 3
3.2 Elaboration of Ru II,II analog of [M3(BTC)2]n
The results summarized in this Chapter 3.2 are initial studies directed to solve the
remaining issues mentioned in Chapter 3.1 and to target Ru II, II analog of [M3(BTC)2]n.
The study mentioned earlier (in Chapter 3.1) involving the investigation of Ru II,III analogs
of HKUST-1 shows rather a complicated picture. As described, the residual acids and the
inevitable counter-ions in the frameworks, to some extent, obstruct the porosity of the
Ru-MOFs. One can imagine that the catalytic activity and the sorption properties of these
materials can be definitely enhanced if the CUSs could be fully available without the
additional coordination (“blocking”) by the counter-ions Y (Cl - , F - , OH - or AcO - , etc.). The
pre-activation procedure (i.e. solvent exchange) helps largely to decrease the
concentration of the incorporated guest molecules such as acetic acid. Getting rid of the
acetic acid as well as the counter-ions are indeed of great importance to elaborate Ru II,II
analog of [M3(BTC)2]n in which the Ru-centers would be the same (in terms of oxidation
state and coordination geometry) as Cu sites in Cu-HKUST-1. One approach to improve
the situation could be the strict exclusion of any additional carboxylic acid as component
of the solvothermal reaction medium. Acid catalysis seems to be needed to facilitate the
coordination equilibria and kinetics of the substitution chemistry at the Ru-centres.
However, every attempt in this direction has not been successful so far (Figure 7.12). On
the other hand, the requirement of avoiding the substitution inert mixed valence Ru II,III -
SBUs for CSA and moving to the Ru II,II -SBUs as well as the strict exclusion of redoxchemistry
(inert conditions) together with any source of coordinating counter-ions Y is
another way to sort out the complexity of the coordination environment (i.e. mixed
valences of Ru centers, residual acids from the starting reactant-solvent and/or the
starting precursors) of the Ru-analogs of HKUST-1.
3.2.1 Synthesis and characterization of SBU-e and Ru-MOF 5
Ru II,II -SBU ([Ru2(OOCCH3)4],SBU-e) was obtained from a blue solution of ruthenium(III)
chloride according to the reported method. [206] The cell parameters obtained from the
single crystal XRD measurements of [Ru2(OOCCH3)4](THF)2 (crystallized from the hot
THF solution) are in a good agreement with the corresponding values communicated in
the literature (Table 7.2). [207] As appeared, prepared complex is air sensitive and loses its
crystallinity after solvent de-coordination. Nonetheless, the FT-IR bands of the symmetric

Intensity, a. u.
Chapter 3 51
and asymmetric COO - vibrations at 1425 and 1541 cm -1 , respectively, match well with the
reported values (Figure 7.10). [82, 208]
Cu-BTC_sim
Cu-BTC_ht
5
Ru II, III -BTC
8 12 16 20 24 28
2, degree
Figure 3.18. PXRD patterns of the activated Ru II,III -BTC 1 and sample 5 in comparison with
simulated patterns of the as-synthesized (Cu-BTC_sim) and activated Cu-BTC (Cu-BTC_ht).
Consequently, degassed solvents (H2O and acetic acid) and inert conditions (Ar
atmosphere) were utilized to synthesize Ru-MOF 5. The PXRD patterns of the activated
mixed-valence Ru II,III -BTC sample obtained in our earlier reports [82, 208] exhibit a little shift
of the peaks in comparison with the simulated PXRD patterns of the Cu-BTC_sim, although
the overall structural integrity is fully preserved. This slight shift stem mainly from the
substitution of the copper-ions by ruthenium-ions (which are of different radii) at the PW
SBUs of the MOF. The PXRD patterns of the prepared here activated sample 5 are in a good
accordance with respective PXRD data of both reported earlier Ru II,III -BTC (Ru-MOF 1)
and Cu-BTC_sim(Figure 3.18), providing a good indication for the phase-purity of the
prepared solid. Furthermore, the IR spectra of the synthesized sample 5 matches well

52 Chapter 3
with that of the Ru II,III -BTC (Figure 3.19). The bands corresponding to the νs(COO) and
νas(COO) vibrations appear at 1359 cm -1 and 1429cm -1 , respectively, suggesting the
coordination of the carboxylate groups of framework BTC. However, presence of
unreacted acetic acid and H3BTC cannot be strictly excluded from IR, as the bands
stemming from C=O stretching in Ru-MOF samples is too small to be distinguished. The
1 H-NMR spectrum of acid-digest sample 5 displays peaks at 8.60 and 1.86 ppm (Figure
7.13). The former resonance is originated from the aromatic protons of BTC. However, the
latter one can be attributed to the protons of acetate, suggesting the presence of AcO(H)
in the obtained sample.
H 3
BTC
(C=O)
Ru II,II
2 (OOCCH 3 ) 4
5
Ru II, III -BTC
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm -1
Figure 3.19. IR spectra of the Ru-BTC 5 in comparison with Ru II,III -BTC 1, [Ru 2 (OOCCH 3 ) 4 ] and
H 3 BTC. The vertical dash line corresponds to the position of ν(C=O) bands.

Chapter 3 53
3.2.2 Investigation on the Ru oxidation state and porosity of Ru-MOF 5
To get more information on the oxidation state of Ru-centers in the obtained sample 5,
XANES spectra on sample 5, Ru II,III -BTC 1, used Ru-precursors (SBU-a and -e) and RuCl3
were subsequently recorded. Due to the differences in position of edge jump different
valences of Ru, the oxidation state of Ru-centers in the MOF structure can be concluded
from the position of the highest peak in the plot of derivative normalized absorption vs.
energy. As illustrated by the Figure 3.20, Ru II,III -BTC 1 shows an edge jump position
between RuCl3 and its starting precursor SBU-a, indicating its mixed valence state, as
documented earlier. [82] To remark, only Ru II was found in the SBU-e. [207] Thus, the same
edge jump position observed in the XANES spectra of the sample 5 suggests the presence
of Ru II -center in the framework structure (Figure 3.20). Consequently, the obtained solid
5 should feature the exact Ru2-PWs as that in HKUST-1 without any counter-ions around.
In the fact, EA results do not reveal the presence of any Cl in the sample Ru-MOF 5, ruling
out the existence of Cl - and RuCl3 in both SBU-e employed during the synthesis and the
obtained solid Ru-MOF 5. A formula of [Ru3(BTC)2]n∙(AcOH)2.3 match well with the
obtained EA results, which could be another sign of the absence of counter-ions. In
comparison with Ru II,III -BTC (1-4) described in Chapter 3.1, the obtained framework turns
to be simpler in the absence any counter-ions, although the presence of acetic acid cannot
be avoided. Furthermore, N2 sorption isotherms collected at 77 K for Ru-MOF 5
demonstrate type I isotherm (Figure 3.21), indicating the microporosity of this material.
Given the greater bulk density of Ru-BTC than Cu-BTC and in order to have a better
comparison with HKUST-1, SBET is calculated in the unit of m 2 /mmol. Thus, SBET of Ru-MOF
5 amounts to 1173 m 2 /mmol, which is quite comparable with the reported value of Cu-
BTC (1049 m 2 /mmol), [83] indicating the same accessibility of Ru-centers as Cu-sites.
Moreover, the axial positions of the diruthemium PW units in the synthesized Ru II,II -BTC
(5) are expected to be open compared to the Ru II,III -BTC, where the presence of counterions
(Cl - , OH - , AcO - ) is needed to balance the charge of [Ru2] 5+ units. The considerably
higher BET surface area (SBET) of Ru II,II -BTC 5 (1371 m 2 /g) than that respective values
reported for Ru II,III -BTC (704-1180 m 2 /g) [82-83, 138, 208] further supports an assumption on
availability of Ru-CUSs in Ru II,II -BTC 5.

54 Chapter 3
Figure 3.20. (a) XANES spectra of the Ru II,III -BTC 1 and Ru II,II -BTC (5) in comparison with
correspondingly employed Ru-precursors (SBU-a and –e) and the commonly used reference
(RuCl 3 ); (b) XANES spectra of Ru II,II -BTC (5) and the employed precursor Ru II,II -SBU
([Ru 2 (OOCCH 3 ) 4 ],SBU-e). The vertical line stands for the same position of edge jump.

V, cm 3 /g
Chapter 3 55
400
350
300
250
200
150
100
/ Ru II, II -BTC
/ Ru II, III -BTC
50
0
0.0 0.2 0.4 0.6 0.8 1.0
relative pressure, p/p 0
Figure 3.21. N 2 adsorption (solid symbols) and desorption (open symbols) isotherms recorded at
77K for the activated Ru II,III -BTC 1 and Ru II,II -BTC (5). Violet circle- Ru II,II -BTC; orange triangle-
Ru II,III -BTC.
3.2.3 Conclusions
Moving from the usage of the mixed-valence Ru II,III -SBUs to the mono-valence Ru II,II -SBU
in CSA, a Ru-analog ([Ru3(BTC)2]n∙(AcOH)2.3) of [Cu3(BTC)2]n has been obtained and
characterized. Interestingly, XANES spectra suggest Ru II,II sites being present in the
structure of the obtained sample 5. Moreover, the BET surface area of this material is the
highest (1173 m 2 /mmol) among of all reported so far Ru-BTC MOFs and quite comparable
with that of HKUST-1 (1049 m 2 /mmol). Thus, Ru II,II -BTC hold a huge perspectives for
various applications in sorption and catalysis. Even more, obtained results are important
for the following studies on related but more complex defect-engineered Ru-MOFs (see
Chapter 4), and elaborated here Ru II,II -SBU is a good candidate for the synthesis of Rubased
MOFs.

4 Linker-based MOF solid solutions: Defect-Engineered MOFs
(DEMOFs) †
Abstract: Employing the mixed-linker solid solution approach, various functionalized ditopic
isophthalate (ip) defect generating linkers denoted as 5-X-ipH2, with X = OH (1), H
(2), NH2 (3), Br (4) have been introduced into [Cu3(BTC)2] (HKUST-1) as well as its mixedvalence
ruthenium-analogue to yield DEMOFs (DE = “defect-engineered”) of the general
empirical formula [M3(BTC)2-x(5-X-ip)xYy]n (M = Ru or Cu, Y = counter-ions, 0 ≤ y ≤ 1.5).
The framework incorporation of 5-X-ip into DEMOFs has been confirmed by a number of
† Most work of this chapter has been covered in the accepted manuscript: W. Zhang, M. Kauer, et al. R. A.
Fischer, Chem. Eur. J. 2016.

Chapter 4 57
techniques. Interestingly, Ru-DEMOF (1c) with 32% framework incorporated 5-OH-ip
reveals the highest BET surface area (1300 m 2 /g, N2 adsorption, 77 K) among all related
samples (including the parent framework [Ru3(BTC)2Yy]n). The characterization data are
consistent with two kinds of structural defects induced by 5-X-ip framework
incorporation: type A, modified paddlewheel nodes featuring reduced metal sites and
type B, missing nodes leading to enhanced porosity. Their relative abundances depend on
the choice of the functional group X in the DLs and its doping level. The defects A and B in
Ru-DEMOFs appear also to play a key role in sorption of small molecules (i.e., CO2, CO, H2)
as well as for the catalytic properties of the samples (i.e., ethylene dimerization and Paal-
Knorr reaction). In addition, synthetic parameters such as anions from the metal salts and
the solvent can also influence the formation of Cu-DEMOFs as well as the generation of
defects.

58 Chapter 4
4.1 Introduction
4.1.1 Solid solutions
Among the well-known mixed-component MOFs, the class of MOF solid solutions (also
known as molecular substitutional alloys) attract huge attention. It implies MOFs where to
two or more types of the related components (either linkers, metals, or both) are
randomly mixed within single-phased framework. Remarkably, this often allows the fine
modulation of the MOF’s functionalities and properties. Considering the nature of the
mixed components, MOF solid solutions could be sub-divided mainly into two groups:
linker-based and metal-based MOF solid solutions. The first group covers MOF solids
where two or more homologous linkers (usually of similar size and functionality) are
integrated in various proportions while the structural integrity of MOF is preserved. The
metal-based MOF solid solutions will be discussed in details in Chapter 5 and involve
mixed-metal frameworks where ions of one metal type is partly isomorphous substituted
by the other metal ions.
Figure 4.1. Mixed-linker approaches to the formation of MOF solid solutions. Magenta balls, metal
nodes; cyan sticks, parent linker; green sticks, isostructural mixed-linker; wine short sticks,
truncated mixed-linker; violet sticks, heterostructural mixed-linker. Inspired by the reports of
Bunck [127] and Fang et al. [137]
Approaches for the synthesis of linker-based MOF solid solutions go basically into three
directions depending on the utilized linker mixtures (Figure 4.1): [127]
i) isostructural mixed-linker (IML) approach where mixed linkers feature identical linking
geometry. [123-124, 209-212]

Chapter 4 59
This is the most straightforward way and commonly used to incorporate some specific
functionality, decorate the walls of a framework with particular (active) organic groups .
Thus, Yaghi’s multivariate MOFs (MTV-MOF-5) are typical representatives of such solid
solutions. [123] In fact, by mixing the terephthalic acid and its derivatives in various
combinations, eighteen single phased MTV-MOFs-5 were prepared and, remarkably,
demonstrated the enhancement of H2 storage capacity as well as adsorption selectivity for
CO2 over CO. Furthermore, Baiker et al. reported mixed-linker amine-functionalized MOFs
(MIXMOFs) with the general formula Zn4O(bdc)x(abdc)3–x (bdc = benzene-1,4-
dicarboxylate; abdc = 2-aminobenzene-1,4-dicarboxylate). Notably, obtained solid
solution materials could be used as both nucleophilic catalysts [124] and support to
immobilize Pd-species for Pd-catalyzed cross-coupling reactions. [212]
ii) truncated mixed-linker (TML) approach, in which one linker is truncated in comparison
with the other.
Figure 4.2. Schematic illustration of the formation of the MOF-5 analogs: spng-MOF-5 and pmg-
MOF-5. Reprinted with permission from K. M. Choi, H. J. Jeon, J. K. Kang and O. M. Yaghi, J. Am.
Chem. Soc., 2011, 133, 11920-11923. Copyright (2011) American Chemical Society. [215]
This strategy is strongly related to the modulation approach, whereby a monocarboxylic
acid is commonly added during the MOF synthesis to influence crystal growth and
morphology. For instance, Kitagawa et al. used acetic acid as a modulator to directly affect
the coordination equilibrium, which in turn controls the crystal growth of nanosized

60 Chapter 4
framework [Cu2(ndc)2(dabco)]n (ndc=1,4-naphthalene dicarboxylate; dabco=1,4-
diazabicyclo[2.2.2]octane). [213] Subsequently, similar morphological control of
[Cu3(BTC)2]n (BTC = 1,3,5-benzenetricarboxylate) from octahedral to cuboctahedral to
cubic by addition of lauric acid has been achieved. [214] Moreover, by utilizing various
amounts of dodecyloxybenzoic acid, Yaghi and co-workers have modified the crystals of
MOF-5 to develop isostructural sponge-/pomegranate- like crystal analogs featuring
meso- and macropores, respectively(Figure 4.2). [215]
iii) heterostructural mixed-linker (HML) strategy, where the employed mixed linkers bear
different linkage geometries. [142, 216-219]
UMCM-1 (University of Michigan Crystalline Material-1) reported by Matzger et al. is a
first rigorous example derived following this approach by the usage of dicarboxylate and
tricarboxylate linkers. This MOF contains 3.1 nm mesoporous hexagonal channels
surrounded by 1.4 nm microporous cages and exhibits exceptionally high surface area. [217]
Thus, variation of the relative lengths of the linkers mixed (di- and trifunctional linkers)
may result frameworks of different topologies. [218] In this manner, HML strategy has
paved up a way to unavailable topologies and larger pore sizes which are not easily
achieved in single-component frameworks. However, careful control over MOF synthesis
to avoid the formation of physical mixtures of different phases needs to be considered.
The latter two synthetic strategies, especially TML approach, can be successfully
employed to prepare defect-engineered MOFs (DEMOFs), which will be described in this
Chapter below.
4.1.2 Defects in MOFs and its “engineering”
It has been recognized that MOFs, similar to other (crystalline) solid-state materials, are
typically not perfect crystals with infinite periodic repetition or ordering of the identical
groups of atoms in space. In fact, defects of various types and length scales (even more
generally: structural heterogeneity) cannot be rigorously avoided during synthesis and
crystal growth and often play an important role for the material properties. [220-222] The
diversity of MOF structures connected with the issues of intrinsic and intentional
structural defects, non-stoichiometry and heterogeneity suggests a much broader
approach for understanding and tailoring their chemical and physical properties. [137] In
fact, Ravon and co-workers has reported MOFs featuring structural defects in which acidic

Chapter 4 61
active catalytic centers were generated through fast precipitation and partial substitution
of dicarboxylic by mono-carboxylic acid linkers. Interestingly, the obtained in this manner
defect-engineered Zn-MOFs show shape selectivity in catalyzing alkylation of large
aromatics molecules. [144] Furthermore, by using CF3COOH and HCl during the synthesis,
Vermoortele et al. demonstrated that UiO-66(Zr) can be modified via partial substitution
of terephthalates by trifluoroacetate. Interestingly, subsequent thermal activation lead to
post-synthetic removal of the trifluoroacetate groups in addition to the dehydroxylation
of the hexanuclear Zr-clusters. All together, this yielded more open defect framework with
a large number of open sites. Remarkably, produced defects at metal sites enhanced UiO-
66(Zr) activity in several Lewis acid catalyzed reactions(Figure 4.3). [141] As a result, better
catalytic performance in several Lewis-acid catalyzed reactions was observed for the
DEMOFs. Controlled introduction and characterization of specific defects into MOFs is
quite a challenge including the comparison with the parent (more or less) “defect-free”
reference samples.
Figure 4.3. The generation of defects in UiO-66(Zr). Reprinted with permission from F.
Vermoortele, B. Bueken, G. Le Bars, B. Van de Voorde, M. Vandichel, K. Houthoofd, A. Vimont, M.
Daturi, M. Waroquier, V. Van Speybroeck, C. Kirschhock and D. E. De Vos, J. Am. Chem. Soc., 2013,
135, 11465-11468. Copyright (2013) American Chemical Society. [141]
[Cu3(BTC)2]n (also known as HKUST-1) [35] as well as the isostructural family [M3(BTC)2]n
(M = Mo, [81, 83] Cr, [78, 83] Ni, [79, 83] Ru, [82-83, 198] Zn, [77, 83] , BTC = benzene-1,3,5-tricarboxylate)
attracted considerable attention over last years, mainly due to presence of coordinatively
unsaturated metal-sites (M-CUS), as has been already introduced in Chapter 3. Intentional
defect generation in [Cu3(BTC)2]n was initially reported by Baiker et al. who studied

62 Chapter 4
partial replacing of BTC by the homologous pyridine-3,5-dicarboxylate (pydc) linker and
revealed enhanced catalytic activity of the modified MOF in the oxidation of benzene
derivatives related to modified M-CUS at the nodes. [136] Subsequently, studies conducted
at our group demonstrated that not only pydc, but also a series of other defect generating
linkers can be framework incorporated in case of [Cu3(BTC)2]n. [139] Interestingly,
functionalized mesopores along with the M-CUS appeared to be generated in such defectengineered
MOFs (DEMOFs) (Figure 4.4).
Figure 4.4. The modulation of the defect structure on the micro- and mesoscales by doping of the
framework with DL. The blue and short red sticks represent perfect and defective linkers. The
yellow and black balls represent perfect and defective metal sites, respectively. The green
highlighted unit indicates parent micropores. Reprinted with permission from Z. Fang, J. P.
Dürholt, M. Kauer, W. Zhang, C. Lochenie, B. Jee, B. Albada, N. Metzler-Nolte, A. Pöppl, B. Weber, M.
Muhler, Y. Wang, R. Schmid and R. A. Fischer, J. Am. Chem. Soc., 2014, 136, 9627-9636. Copyright
(2014) American Chemical Society. [139]
In parallel, Hupp et al. gave an account of the enhanced porosity by introducing
isophthalate (ip) into [Cu3(BTC)2]n. [140] The concept of defect engineering by a mixed
component approach using fragmented linkers together with the parent one was also
expanded to the isostructural Ru-analogue. [138] Ru-DEMOFs [Ru3(BTC)2-x(pydc)xYy]n (Y =
counter-ion, Cl - , OH - , OAc, etc.; 0 < y≤ 1.5) were obtained through direct mixing of H2pydc
and H3BTC in one-step solvothermal synthesis. The generation of reduced Ru δ + (0

Chapter 4 63
compared with the parent material, the actual compositions of these Ru-DEMOFs are very
difficult to establish and are not entirely clear. This stems from the structural complexity
of such multi‐component solid solution MOFs and a range of possible compositional
variations, which are not mutually exclusive (counter-ions, residual synthesis
components such as linkers, coordination modulators etc.).
Figure 4.5 Design concept of the DEMOFs applying the mixed component/fragmented linker solid
solution approach and sketch of the two possible, most important paddlewheel-node related
defects.
Figure 4.5 summarizes the concept of defects introduction into mixed-valence
[M3(BTC)2Yy]n by using divalent isophthalate linkers as fragmented variants of trivalent
BTC. Mainly, two types of defects need to be distinguished: Type A refers to structurally
and electronically modified paddlewheel units (missing one carboxylate ligator function),
in which (at least) one out of the four bridging carboxyl groups from the parent BTC linker
in the regular paddlewheels has been partly substituted by the (neutral) functional group
of the DL. Consequently, for charge compensation, the metal sites could be either partly
reduced (mixed-valence state) or may carry additional anionic (mono-valent) ligands
(Y) [137-138] However, apart from such type A, defects of type B could be formed, where
whole paddlewheel nodes are eliminated from the structure, as it has been demonstrated

64 Chapter 4
in the case of ip introduction into [Cu3(BTC)2]n. [140] It is conceivable, that such missing
node defects could be formed in a correlated fashion during the MOF crystal growth
process and in such a case larger areas of missing nodes may be generated to yield
mesopores.

Chapter 4 65
4.2 Ruthenium Metal-Organic Frameworks featuring Different Defect Types
Being mainly studied in Cu-HKUST-1, a comprehensive understanding of the nature and
formation of different types of isolated local and larger scale correlated defect sites in
DEMOFs of the [M3(BTC)2]n family and MOFs in general is very limited and this research
is still at its infancy. [137] The work in this chapter is a follow-up of the previous
investigations on defect engineering in [Ru3(BTC)2Yy]n using H2pydc as (single) defect
generating linker. [138] Similar to the previous more elaborate study on defect-engineered
Cu-HKUST-1 [139] , a series of 5-X-isophthalic acids (5-X-ipH2, X = OH, H, NH2, Br) are
selected and mixed them with H3BTC to yield the Ru-DEMOFs of the general formula
[Ru3(BTC)2-x(5-X-ip)xYy]n (Figure 4.5). The choice of the functional group X in DL is on the
basis of two aspects: i) modulating the coordination binding strength between linkers and
Ru-nodes, namely, changing one of the carboxylate group in parent H3BTC linker to
weaker binding groups (OH, NH2) or even inert coordination groups (H, Br); ii) labeling
DL with easily tracked elements such as Br, NH2, etc. for analytical purpose. Thus, a
number of complementary characterization methods are applied to obtain compositional
and microstructure data of the materials. The aim is to at least qualitatively assess the
tendency of type A and type B defect formation as a function of synthetic conditions and
the chosen 5-X-ip linker. Several catalytic reactions, such as ethylene dimerization and
Paal-Knorr reaction (usually running under Lewis acidic conditions) as well as low
temperature CO2→CO dissociative chemisorption in the dark under UHV conditions, have
been chosen as test reactions to monitor the influence of defects on the performance of
the Ru-DEMOFs.
4.2.1 Synthesis and characterization of the Ru-DEMOF materials
In the following, a comprehensive account on the conducted experiments, obtained
analytical and characterization data is provided for elucidation of the defect structure of
Ru-DEMOFs of the general formula [Ru3(BTC)2-x(5-X-ip)xYy]n. The main goal of the
presented study is to substantiate the hypothesis of type A and type B defect formation in
these systems as introduced above (Figure 4.5).

66 Chapter 4
4.2.1.1 Crystallinity and stability of the obtained samples
Figure 4.6. PXRD patterns of the solvated Ru-DEMOF materials 1a-1d, 2a-2d, 3a-3d, 4a-4c
compared with the solvated parent Ru-MOF, respectively. 1a-1d: DL is 5-OH-ip; from 1a to 1d,
feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 2a-2d: DL is ip; from 2a-2d,
feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 3a-3d: DL is 5-NH 2 -ip, from 3a to
3d, feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 4a-4c: DL is 5-Br-ip, from 4a
to 4c, the feeding level is increasing: 10%, 20%, 30%, respectively. Vertical lines at 42.1°and 44°
stand for the respective reflections of (001) and (101) faces of hexagonal close‐packed metallic
Ru-particles or Ru-NPs.
Parent Ru-MOF in this chapter for comparison was prepared according to the synthetic
method for Ru-MOF 1_ex in Chapter 3. All Ru-DEMOF samples were obtained according
to the previously published procedure, [138] using [Ru2(OOCCH3)4Cl]n, H3BTC and defect
generating 5-X-ipH2 as starting materials in the acetic acid/water solution under
solvothermal conditions. The sample-numbering scheme is based on the framework

Chapter 4 67
incorporated 5-X-ip linker: X= OH (1), H (2), NH2 (3) or Br (4). Further labeling (a, b, c
etc.) refers to various levels (molar%) of DL incorporation. The PXRD patterns of the assynthesized
and activated samples indicate that all materials (except 2d) are crystalline
and isostructural with the parent Ru-MOF that is obtained employing the same method
with H3BTC, only (Figures 4.6 and 4.7). It should be noted that Ru 2+/3+ ions can be possibly
reduced to eventually yield metallic ruthenium. Therefore, the solvothermal synthesis
Figure 4.7. PXRD patterns of the activated Ru-DEMOF materials 1a-1d, 2a-2d, 3a-3d, 4a-4c
compared with the solvated parent Ru-MOF, respectively. 1a-1d: DL is 5-OH-ip; from 1a to 1d,
feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 2a-2d: DL is ip; from 2a-2d,
feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 3a-3d: DL is 5-NH 2 -ip, from 3a to
3d, feeding level is increasing: 10%, 20%, 30%, 50%, respectively. 4a-4c: DL is 5-Br-ip, from 4a
to 4c, the feeding level is increasing: 10%, 20%, 30%, respectively. Vertical lines at 42.1°and 44°
stand for the respective reflections of (001) and (101) faces of hexagonal close‐packed metallic
Ru-particles or Ru-NPs.
conditions have to be carefully monitored. However, no PXRD-peaks in the 2θ range of 40-
45° were found, neither for the as-synthesized nor for the activated samples, thus

68 Chapter 4
suggesting the absence of a substantial amount of Ru 0 nano-particles (Ru-NPs).
Reflections at 42.1°and 44°are usually assigned to (001) and (101) faces of hexagonal
close‐packed metallic Ru-particles or Ru-NPs. [223] Further data to rule out Ru 0 , XANES in
particular, will be described below. The corresponding results provide additional
evidence for the absence of Ru/RuOx‐NPs in the obtained Ru-DEMOFs. With the exception
of 2d, thermal gravimetric analysis (TGA) shows no decomposition of the prepared
materials for temperatures below 250 °C, suggesting that thermal stability of Ru-DEMOFs
is preserved as compared to the parent MOF (Figure 4.8).
Figure 4.8. TG curves of the prepared Ru-DEMOFs 1a-1d (with 5-OH-ip DL), 2a-2c (with ip DL),
3a-3d (with 5-NH 2 -ip DL), 4a-4c (with 5-Br-ip DL) in comparison with the parent Ru-MOF,
respectively.

Chapter 4 69
4.2.1.2 The incorporation amount of DLs as well as the composition of the
materials
The incorporation and quantification of DLs have been initially testified by NMR
spectroscopy of the digested samples after activation and the assessment of porosity
(Table 4.1). Thus, in the 1 H-NMR spectra of the samples 1a-d, appearance of two
additional peaks (compared with the parent Ru-MOF) at 7.51 ppm and 7.89 ppm is clearly
seen (Figure 4.9). These two resonances can be assigned to the aromatic protons of 5-OHip
linkers. Expectedly, upon increasing the feeding amount of the DL (5-OH-ipH2), the
intensities of its characteristic resonances also increases in the digested sample solution.
Figure 4.9. 1 H-NMR spectra of the Ru-DEMOFs (1a-1d) digested in DCl/DMSO-d 6 mixture. DL is
5-OH-ip. H 3 O + comes from H 2 O and HCl contained in DCl. Due to the sensitivity of H 2 O peak to the
solution conditions, the proton resonance of H 3 O + varies here in the range of 4-6 ppm, dependent
on pH value of the total solution.

70 Chapter 4
Table 4.1. The molar fractions (%) of the DLs used for the synthesis and observed in the final Ru-
DEMOFs in respect to the total amount of linkers (H 3 BTC + 5-X-ipH 2 = 100%). The values were
obtained from the integrals of proton peaks in 1 H-NMR spectra of the acid-digest sample. For the
samples 1a-1d DL is 5-OH-ip; for 2a-2c – ip; for 4a-4c – 5-Br-ip, respectively.
Sample
Feeding
(used for synthesis)
Obtained
1a 10% 8%
1b 20% 20%
1c 30% 32%
1d 50% 37%
2a 10% 15%
2b 20% 28%
2c 30% 47%
4a 10% 17%
4b 20% 25%
4c 30% 42%
A similar scenario was observed also for the samples with ip DL (series 2a-c). Resonances
corresponding to the protons of ip are seen at 8.4 ppm, 8.1 ppm and 7.6 ppm (Figure 4.10).
The framework incorporation amount of ip in 2a-c increases upon increasing the
concentration of the DL in the reactant solutions. However, the incorporated amount of ip
was found to be higher than expected from the H3BTC:H2ip feeding ratio, which is in
contrast with that in the case of Ru-DEMOF series 1 where the incorporation of 5-OH-ip
stay the same (or a little less) than the feeding concentration in the starting reactants. This
result might be attributed to the slightly different coordination equilibria that correlate
with the Brønsted acid dissociation constants of the used linkers: pKa (H3BTC) = 3.12,
3.89, 4.70 and pKa (H2ip) = 3.46, 4.46. [224] However, the pKa differences are small and a
conclusive explanation based on pKa is not straightforward. Dincă et al. argued that
deprotonated BTC could serve as a counter-ion to provide the charge balance of [Ru2] 5+
units in Ru-analogue of Cu-HKUST-1. [83] From our earlier investigation we concluded that
H3BTC is present in the pores of [Ru3(BTC)2Yy]n in the form of fully protonated species,
rather than as deprotonated counter-ions. [208] Both studies indicate that the linker used
for the synthesis could still be present in the obtained materials. Hence, it is conceivable
that the defect generating H2ip linker can also reside either as a counter-ion or as a guest

Chapter 4 71
molecule in the pores of the Ru-DEMOFs (2a and 2b). On the basis of these arguments it
can be understood why the amount of incorporated ip can be higher than expected from
the H2ip:H3BTC feeding ratio. Indeed, very weak IR-bands in the range of ν(C=O), ν(C=C)
or νas(COO) vibrations (1736-1521 cm -1 ) have been observed in case of samples 2a-2d.
However, the small separation of the ν(C=O) bands of non-coordinated acetic acid (1715-
1640 cm -1 ), [225] protonated/non-coordinated H2ip (1670 cm -1 ) and H3BTC (1680 cm -1 )
(see Figure 4.11.2) makes it hard to unambiguously determine the exact origin of these
weak vibrations.
Figure 4.10. 1 H-NMR spectra of the Ru-DEMOFs (2a-2c) digested in DCl/DMSO-d 6 mixture. DL is
ip. H 3 O + comes from H 2 O and HCl contained in DCl. Due to the sensitivity of H 2 O peak to the
solution conditions, the proton resonance of H 3 O + varies here along with the variation of pH value
of the total solution.

72 Chapter 4
Figure 4.11. IR spectra of the prepared Ru-DEMOFs 1a-1d (with 5-OH-ip DL), 2a-2d (with ip DL),
3a-3d (with 5-NH 2 -ip DL), 4a-4c (with 5-Br-ip DL) in comparison with the parent Ru-MOF and
the corresponding DL used in the synthesis, respectively. The vertical dash lines in Figure 4.11.3
indicate position of the vibrations of N-H and C-N bonds.
Here it should be pointed out that in all 1 H-NMR spectra of the digested Ru-DEMOF
samples the resonance at ca. 1.91 ppm, originated from the –CH3 groups of acetate, has
been detected. This is in line with our previous investigations on the parent single-linker
Ru-MOFs obtained from various Ru-precursors and the Ru-DEMOFs with pydc DL, where
the same resonance due to acetate in the digested samples with the molar ratio of
n(AcO):n(BTC) in the range from 0.7 to1.8 was always observed as well. [138, 208] . We
anticipate three main origins of the presence of acetate in the discussed Ru-MOFs:
i) it may act as a counter-ion to compensate the overall charge of the framework (Figure
4.12a);

Chapter 4 73
ii) owing to the competition with BTC and 5-X-ip, it could be residual/non-substituted and
paddle wheel coordinated acetate-groups of the used Ru-precursor ([Ru2(OOCCH3)2Cl]n)
(Figure 4.12b);
Figure 4.12. Schematic representation for the two possible origins of acetate in the Ru-DEMOFs.
iii) finally, it might reside as AcOH in the pores of the framework through weak
interactions and, therefore, cannot be easily removed by washing and subsequent thermal
activation (i.e., heating at 150 °C under dynamic vacuum).
To recall, the glacial acetic acid/water mixture (AcOH:H2O = 0.05:1) was found to be
essential for a successful synthesis and was always used for all reported Ru-(DE)MOFs
(see Experimental Section). Besides, employed linkers may also serve as guest molecules
as has been mentioned above. Attempts to evaluate the presence of acetic acid and linkers
from the IR spectra is not quite feasible due to the overlapping of the bands of νas(COO)
and νs(COO) (coordinated in a bidentate-bridging mode and free-coordinated carboxylate
group) [226] as well as low intensity of the respective bands. Although one can monitor
acetate groups in IR-spectroscopy by employing F-labled acetate (eg. perfluoro-acetate
instead of acetate) for synthesis, [227] the crucial synthesis parameters of Ru-MOFs make
this attempt impossible. Earlier effort of using various acids as the reaction solvent failed
to form crystalline parent Ru-MOF. [208] Consequently, the presence of acetate (mainly)
and non-reacted free linkers used in Ru-DEMOFs raises questions about the actual sample
compositions and local structures and, thus, causes more complications with ambiguous
interpretation of the analytical data than in case of the homologous Cu-DEMOFs. [139] The
compositions of the Ru-DEMOFs samples discussed in this work have been derived by

74 Chapter 4
taking into account the complete set of experimental results and a full account is given in
Tables 4.2 and 4.3).
Table 4.2. Elemental analysis results (calculated and found) of the activated Ru-DEMOFs (1a, 1c
and 1d) in comparison with the parent Ru-MOF. Molar ratio of Ru : Cl calculated based on the
found mass percentages are also given below.
Sample
C, wt % H, wt % Ru, wt % Cl, wt %
cal. found cal. found cal. found cal. found
Ru : Cl
parent 28.5 27.26 2.31 1.65 31.40 30.45 3.67 3.41 3: 1
1a 29.3 28.4 2.28 1.49 31.55 30.08 3.69 3.47 3: 1
1c 31.67 31.26 1.89 1.37 32.03 31.08 3.37 3.27 3: 0.9
1d 30.26 29.43 2.06 1.59 31.36 30.41 3.30 3.35 3: 0.9
Table 4.3. Proposed formula* and the molecule weight of the activated Ru-DEMOFs (1a, 1c and
1d) as well as the parent Ru-MOF.
Sample
Parent Ru-
MOF 1_ex
1a
1c
1d
Formula
[Ru 3 (C 9 H 3 O 6 ) 2 Cl(CH 3 COO) 0.5 ]·(CH 3 COOH) 1.5 (C 9 H 6 O 6 ) 0.1 (H 2 O) 4
([Ru 3 (BTC) 2 Cl(AcO) 0.5 ]·(AcOH) 1.5 (H 3 BTC) 0.1 (H 2 O) 4 )
[Ru 3 (C 9 H 3 O 6 ) 1.84 (C 8 H 3 O 5 ) 0.16 Cl(OH) 0.5 ]·(CH 3 COOH) 2.8 (H 2 O) 2
([Ru 3 (BTC) 1.84 (5-OH-ip) 0.16 Cl(OH) 0.5 ]·(AcOH) 2.8 (H 2 O) 2 )
[Ru 3 (C 9 H 3 O 6 ) 1.36 (C 8 H 3 O 5 ) 0.64 Cl 0.9 (OH) 0.6 ]·(CH 3 COOH) 2.2 (C 8 H 6 O 5 ) 0.4
([Ru 3 (BTC) 1.36 (5-OH-ip) 0.64 Cl 0.9 (OH) 0.6 ]·(AcOH) 2.2 (5-OH-ipH 2 ) 0.4 )
[Ru 3 (C 9 H 3 O 6 ) 1.26 (C 8 H 3 O 5 ) 0.74 Cl 0.9 (OH) 0.6 ]·(CH 3 COOH) 1.3 (C 9 H 6 O 6 ) 0.5 (H 2 O) 2.5
([Ru 3 (BTC) 1.26 (5-OH-ip) 0.74 Cl 0.9 (OH) 0.6 ]·(AcOH) 1.3 (H 3 BTC) 0.5 (H 2 O) 2.5 )
Molecular
weight
965.6
961.1
946.6
982.6
* The proposed formula of all the samples above have been calculated according to the facts and
considerations listed below:
Parent (BTC) to DL (5-OH-ip) ratios have been calculated based on the 1 H-NMR spectra (i.e.,
integration of the linker-related signals) of the respective acid-digested samples.
The parent Ru-MOF and reported Ru-DEMOFs are isostructural. At this point it is hard to
quantitatively estimate contribution from the defects B (missing metal-nodes), therefore, for initial
evaluations assumption that the general composition of the prepared solids is [Ru3(L)2Yy]n (L = total
linker amount) was employed. Thus, the Ru : L molar ratio can be taken as a fixed value – 3 : 2.
Further, having in mind there is generally 3 molar equivalents of Ru per 1 molecular unit of MOF,

Chapter 4 75
the Cl-amount was subsequently calculated based on the measured EA values and respective Ru :
Cl ratios.
As observed by the 1 H-NMR, TG and IR analyses, the contribution of the counter-ions and guest
molecules are mainly from Cl, OH, acetate, H2O and used linkers. In analogy to the previously
reported parent Ru-MOF [208] and the Ru-DEMOF with pydc DL, [138] in the currently discussed Ru-
DEMOFs acetic acid is also present, which is clearly evidenced by the 1 H-NMR spectra of the
digested samples. To note, the amount of the acetic acid can be considerably reduced by additional
solvent exchange procedure, namely, soaking of the activated samples in a large amount of water
while intense stirring to exchange the residue acetic acid. However, the risk of leaching out of Ru
needs also to be taken into account here. [208] Hence, our current studies dealt with the obtained
powders applying gently water soak as solvent exchange procedure to decrease the residue of the
acetic acid. And the overall concentration of the acetic acid decreased in comparison with our
previously report on the Ru-DEMOF with pydc DL in spite of the slightly decrease of Ru content.
In addition of the multiple possible status of acetic acid, starting reactant (i.e. linkers) can be also
accommodated into the framework as guest molecules or served as counter-ions, since based on
the NMR data the amount of the DL in some cases appeared to be higher than its respective feeding
amount. Besides, minor quantities of the coordinated H2O might be occluded / resided in the pores
as well, as the TG curves of the activated samples show the slight decrease in the range of 100-250
°C.
Figure 4.13. EDX spectra of the Ru-DEMOFs 4a-4c (with 5-Br-ip DL). The detection of Br
clearly indicates the presence of the employed DL.

76 Chapter 4
As quantitative digest of the samples 3a-d is not sufficient, detection and determination
of the DL contents (5-NH2-ip) from 1 H-NMR measurements was not possible.
Nevertheless, the IR spectra of these samples provide a qualitative evidence for the 5-NH2-
ip incorporation. Indeed, the observed bands at 1651 cm -1 and 1264 cm -1 stem from δ(N-
H) and ν(C-N) vibrations of the 5-NH2-ip (Figure 4.11). In case of the 5-Br-ip (samples 4ac),
the gradual increase of intensities of the respective signals in both 1 H-NMR and TEM-
EDX spectra suggests the presence of DL in these Ru-DEMOFs (see Figures 4.13 and 4.14).
Figure 4.14. 1 H-NMR spectra of the Ru-DEMOFs (4a-4c) digested in DCl/DMSO-d 6 mixture.
DL is 5-Br-ip. H 3 O + comes from H 2 O and HCl contained in DCl. Due to the sensitivity of H 2 O
peak to the solution conditions, the proton resonance of H 3 O + varies here, dependent on pH
value of the total solution.
4.2.2 Porosity of Ru-DEMOF samples and the confirmation of the DL incorporation
To support further the framework incorporation of the DL and rule out its extra
framework inclusion within the pores in a high quantity, we have carried out N2 sorption
measurements for the activated samples. The N2 sorption isotherms at 77 K for all samples

Chapter 4 77
Figure 4.15. N 2 sorption isotherms collected at 77 K for Ru-DEMOF samples 1a-1d, 2a-2c, 3a-3d,
4a-4c. 1a-1d: DL is 5-OH-ip, incorporation amount is 8%, 20%, 32% and 37%, respectively; 2a-
2c: DL is ip, incorporation amount is 15%,28% and 47%, respectively; 3a-3d: DL is 5-NH 2 -ip; 4a-
4c: DL is 5-Br-ip, incorporation amount is 17%, 25% and 42%, respectively. Closed and open
symbols represent the adsorption and desorption isotherms, respectively. Black circles – parent
Ru-MOF; blue triangles – a samples of the respective series 1-4; dark cyan diamonds – b samples
of the respective series 1-4; magenta squares – c samples of the respective series 1-4; dark yellow
stars – d samples of the respective series 1-4.
(1a-d, 2a-d, 3a-d and 4a-c) reveal type I isotherm without any hysteresis loop (Figure
4.15), indicating that all Ru-DEMOFs are microporous materials. [228] In general, while
comparing with the Brunauer-Emmett-Teller (BET) surface area (SBET) of the parent Ru-
MOF (998 m 2 /g), one can consider Ru-DEMOFs being analogous when the value (SBET) is
in/above the range of the parent one. In other words, the considerably high SBET of the
discussed Ru-DEMOFs rules out substantial guests occlusion and pore blocking such as by
non-reacted DLs, acetate or Ru/RuOx‐NPs. Interestingly, when 5-OH-ipH2 is used as DL,
SBET of the Ru-DEMOFs gradually increases until 5-OH-ip is incorporated up to 32% (1c)

78 Chapter 4
(Figure 4.16). Notably, the SBET of this sample 1c is the highest among all [Ru3(L)2Yy]n (L =
linker) isostructural MOFs (including the single-linker and other mixed-linker Ru-
DEMOFs reported so far). [82, 138] This indicates that the 5-OH-ip is a good candidate for
defects engineering in Ru-MOFs.
Figure 4.16. The variation of the BET surface area (S BET ) derived based on measured N 2 sorption
isotherms (77 K) upon increase of the DL doping. 'Parent' stands here for parent single-linker Ru-
MOF (with only BTC). In the samples 1a-1d, 5-OH-ip serves as a DL; 2a-2c – ip; 3a-3d – 5-NH 2 -
ip; 4a-4c – 5-Br-ip, respectively. The values of S BET have been summarized in Table 7.4 in Chapter
7.
In contrast with the Ru-DEMOFs series 1 with 5-OH-ip DL, the integration of the ip DL
generally results in lower porosities, as demonstrated by the results for samples 2a-d.
However, the SBET of samples 2a and 2b are still higher than the SBET of the parent Ru-MOF.
Nonetheless, upon increasing the ip content, the surface area decreases. Thus, considering
porosity characteristics, the optimum incorporation extent of DL in these series stays at
28% (sample 2b). In case of 5-NH2-ip DL, the porosity of the Ru-DEMOFs (3a-c) is fully
maintained, while increasing of the feeding level to 50% leads to porosity decrease
instead (sample 3d, SBET = 781 m 2 /g). These observations in 2a-d and 3a-d series are
probably due to the accommodation of unreacted 5-X-ipH2 in the pores. Along with the

Chapter 4 79
increasing feeding of 5-X-ipH2 the competition between BTC and 5-X-ip increases.
Subsequently, it is more difficult to rule out the presence of unreacted 5-X-ipH2 as the
reason of the decreasing SBET. In the same line of reasoning, the SBET of the samples 4a-c
dramatically decreased from 996 to 693 m 2 /g. Hence, the optimized incorporation of 5-
Br-ip can only reach up to 17% (4a). Notably, in our previous studies on the defectengineered
Cu-HKUST-1, the generation of mesopores was observed. [139] Curiously, in the
present case of the homologous Ru-DEMOFs, an opposite trend was observed, which
might be attributed to the preference of isolated defects rather than to the correlated
defects in the framework (Figure 4.17). During the formation of Ru-DEMOFs, the
substitution of [Ru]-L + DL ⇌ [Ru]-DL +L (L = AcO/BTC, DL = 5-X-ip) is kinetically
hindered by higher activation energy in comparison to that in the case of Cu-DEMOFs.
Consequently, the substitution is possibly much slower and lead to only isolated defects.
Figure 4.17. Schematic representation of point defects and correlated defects in DEMOFs. Figure
is provided by Dr. O. Halbherr.
4.2.3 XANES, XPS and UHV-FTIR studies: ruthenium oxidation state variation as
indication of defect type formation
As earlier mentioned, in our previous studies on doping of the Ru-MOF with defect pydc
linker, we have assigned the introduced local defects, according to Baiker et al., [136] as
modified Ru-paddlewheels with three coordinating BTC and one pydc linker, in which the
pyridyl-N site acts as a weakly binding ligator-site over the Ru-dimer. Such structural
irregularities are associated with (partially) missing linker function (i.e., carboxylate) and
consequently steric and electronic modification of the Ru-SBUs (see Figure 4.5).
Additionally, partial ruthenium reduction has been observed. Namely, apart from the
expected Ru 2+ and Ru 3+ (as in the parent Ru-MOF), we revealed also distinctly reduced

80 Chapter 4
framework Ru-species (Ru δ+ , 0

Chapter 4 81
XANES spectra (Figure 4.18) show deviation of the edge jump derivative for the samples
1a-d from that one of the parent Ru-MOF. For 1a-c, the position of edge jump gradually
shifts to the lower energies, suggesting reduced Ru-sites with oxidation states lower than
2+ or 3+. We relate this observation to the generation of defects A in the samples 1a-c.
However, the position of the edge jump in case of the sample 1d moved again to higher
energies, illustrating that the amount of reduced Ru-species is now decreased with
respect to samples 1a-c. The different tendency suggests that defects B may also be
created when 5-OH-ip linker was incorporated into the framework at ratios higher than
32%. The same trend has been observed for the 5-NH2-ip linker (samples 3a-c). Indeed,
the XANES spectra of the samples 3a-b suggest again the presence of reduced Ru δ+
(0

82 Chapter 4
Figure 4.20. XANES spectra of the parent Ru-MOF and Ru-DEMOF sample 4a (with 17% 5-Br-ip
DL, derivative of the normalized intensity vs. Energy). Black: parent Ru-MOF; blue: 4a.
Figure 4.21. XANES spectra (derivative of the normalized intensity vs. Energy) of the Ru-DEMOF
materials 2a and 2b compared with the parent Ru-MOF. Black: parent Ru-MOF; blue: 2a (15% ip);
dark cyan: 2b (28% ip)..

Chapter 4 83
Interestingly, the position of the edge jump in case of the ip-doped samples 2a-b does not
change compared with that in the parent Ru-MOF (Figure 4.21). The Ru oxidation state is
not affected by the incorporation of ip, which could be taken as indication of a
predominance of defects B for samples 2a-b. When the functional group of the DLs
changes from small, coordinative inert H to the somewhat larger and coordinative more
suitable ligator-sites like -OH, -NH2 or -Br, the defects A are favored in case of relatively
low doping level. However, upon rising the doping level, defects B are increasingly created
along with some remaining defects A, resulting in less pronounced variation of the
oxidation state of Ru in the defect-engineered samples compared with the parent material.
Figure 4.22. XANES spectra (normalized absorption vs. Energy) of the Ru-DEMOF materials (1a-
1d, 2a, 2b, 3a-3c and 4a) compared with the parent Ru-MOF as well as some Ru references. Solid
Black: parent Ru-MOF; solid blue: a samples of the respective series 1-4; solid dark cyan: b
samples of the respective series 1-4; soid magenta: c samples of the respective series 1-4; solid
dark yellow: d samples of the respective series 1-4; dash dot violet: Ru; solid orange: RuO 2 ; short
dash wine: Ru nano-particles(NPs).

84 Chapter 4
It is important to note that the white line in the XANES spectra (normalized absorption vs.
energy, Figure 4.22) of all the Ru-DEMOFs samples as well as the parent Ru-MOF are
strikingly different from those measured for the Ru-NPs, metallic Ru and RuO2. These
observations support PXRD results (see above and Figures 4.6 and 4.7) and allow also to
rule out the presence of other Ru-phases as significant impurities in the Ru-DEMOFs
including parent Ru-MOF. [223] Thus, we assume that it is valid to assign all Ru-species to
the metal-nodes of the frameworks. Further information on the local environment of Ru
can be obtained also from EXAFS. The analysis of the experimental data is, however, a
formidable effort, since many different models for Ru-DEMOFs have to be considered and
a variety of local structures may be present in parallel in the samples as discussed before.
Therefore, a thorough analysis of the EXAFS-data is outside the scope of this dissertation
project.
The different samples fabricated in this study have also been characterized using Highresolution
X-ray photoelectron spectroscopic (XPS) in order to confirm the assignments
based on XANES and for a more quantitative estimation of the relative abundance of the
different Ru-species (Ru 3+ , Ru 2+ and Ru δ+ ) in the Ru-DEMOFs. The samples 1a, 1c, 1d, 2a
and 2b with 5-OH-ip and ip DLs, respectively, have been selected. Remarkably, similar to
the related pydc-doped Ru-DEMOFs we elaborated earlier, [138] reduced Ru δ+ -species have
been found in the Ru-DEMOFs (samples 1a, 1c and 1d) in addition to the Ru 2+ - and Ru 3+ -
species. Two Ru 3d doublets (3d5/2 and 3d3/2) at ca. 281.6 and 285.8 eV as well as at 282.6
and 286.8 eV, attributed to the Ru 2+ - and Ru 3+ -species, respectively, are seen in the
deconvoluted XP spectra of all measured samples (Figure 4.23). In addition, another Ru
3d doublet appears at ca. 280.5 and 284.7 eV in the Ru-DEMOFs samples 1a, 1c and 1d.
On the basis of quantitative estimations of the XP spectra, some variation of the Ru 3+ /Ru 2+
ratio and, in particular, reduction to Ru δ+ in 1a, 1c and 1d can be clearly seen (Table 4.4).
From the parent Ru-MOF to the Ru-DEMOF sample 1a, the ratio of Ru 3+ / Ru 2+ / Ru δ+ varies
from 1 / 1.24 / 0 to 1 / 1.75 / 0.08, indicating that the incorporation of DL induces partial
ruthenium reduction (i.e., relative concentrations of the Ru 2+ and Ru δ+ increase).
Moreover, upon increasing the incorporation level of 5-OH-ip to 32% for 1c (feeding level
30%), the amount of the reduced Ru δ+ -species considerably increases to the highest value
(Ru 3+ / Ru 2+ / Ru δ+ = 1 / 1.69 / 0.59) among all studied samples. Importantly, the Ru δ+ -
related doublet decreases significantly in intensity with further increase of the
incorporation to 37% for 1d (feeding level 50%). This is in contrast to the observation for

Chapter 4 85
Figure 4.23. Deconvoluted XP spectra of the Ru-DEMOFs samples (A)1a (8% of 5-OH-ip), 1c (32%
of 5-OH-ip) and 1d (37% of 5-OH-ip), (B) 2a (15% of ip) and 2b (28% of ip) in Ru 3d and C 1s
regions in comparison with parent Ru-MOF. Original figures are provided by P. Guo.
pydc-doped Ru-DEMOFs, where a continuous rise of the Ru δ+ signals was detected along
with increasing degree of pydc incorporation. [138] The relatively lower concentration of
Ru 2+ and Ru δ+ in 1d (Ru 3+ / Ru 2+ / Ru δ+ = 1 / 1.23 / 0.09), as compared to the respective
ratios estimated for 1c, can be explained by our assumption of simultaneous generation
of both defects A and B with distinct preference of B over A at higher feeding
concentrations of 5-OH-ip. Interestingly, for the ip-doped samples 2a-b no highly reduced

86 Chapter 4
Ru δ+ have been observed in the XP spectra (no Ru3d doublets at ca. 280.5 and 284.7 eV;
Figure 4.23). These data confirm the assignment deduced from XANES data, suggesting
that application of DL with the coordinatively inactive functional group H (2a-b) is likely
to more selectively induce missing node defects B in the Ru-DEMOFs without Ru
reduction (as this is indicative for a type A defect). According to the results of XANES and
XPS, we thus conclude that the Ru-DEMOFs materials with 5-X-ip (X= OH, NH2 and Br)
contain predominantly defects A, especially at moderate incorporation levels. However,
the simultaneous generation of defects B in these samples is also likely as indirectly
deduced from the non-linear dependence of the XANES and XPS data on the doping level.
Table 4.4. The assignments of binding energies as well as the ratio of Ru 3+ / Ru 2+ / Ru δ+ (calculated
from the deconvoluted spectra) in the parent Ru-MOF sample and Ru-DEMOFs (1a, 1c 1d, 2a and
2b). 1a, 1c and 1d - 8%, 32% and 37% of 5-OH-ip, respectively; 2a and 2b - 15% and 28% of ip,
respectively. Data provided by P. Guo.
Sample Binding energy, eV Assignment Ru 3+ / Ru 2+ / Ru δ+ ratio
Parent Ru-MOF
1a
1c
1d
2a
285.86 / 281.66 Ru 2+
286.86 / 282.66 Ru 3+
285.86 / 281.66 Ru 2+
286.86 / 282.66 Ru 3+
284.65 / 280.45 Ru δ+
285.71 /281.51 Ru 2+
286.71 / 282.60 Ru 3+
284.60 / 280.40 Ru δ+
285.72 / 281.52 Ru 2+
286.72 / 282.52 Ru 3+
284.65 / 280.45 Ru δ+
285.86 /281.66 Ru 2+
286.86 / 282.66 Ru 3+
1 / 1.24 / -*
1 / 1.75 / 0.08
1 / 1.69 / 0.59
1 / 1.23 / 0.09
1 / 1.73/ -*
285.88 / 281.68 Ru 2+
2b
286.88 / 282.76 Ru 3+
* no species have been determined.
1 / 1.42 / -*
Consequently, UHV-IR spectroscopic investigations employing CO as a probe molecule
have been carried out on two representative samples 1c and 1d to gain complementary

Chapter 4 87
evidence on the valence states of framework Ru sites and the associated defect types.
Parent Ru-MOF was reported to reveal bands at 2172 and 2127 cm -1 , arising from CO
interactions with Ru 3+ and Ru 2+ , respectively (Figure 4.24). [138] Apart from these two
bands, the spectra of the samples 1c and 1d show additional bands at 2041 and 1998 cm -
1 , which can be attributed to CO bound to reduced Ru δ+ (0

88 Chapter 4
Figure 4.25. UHV-IR spectra of Ru-DEMOF 1c and 1d compared with parent Ru-MOF and Ru-
DEMOF with 30% pydc incorporation upon CO 2 dosing at 90-95 K after annealing the sample at
475-500 K. The bands at 2041 cm -1 and 1993 cm -1 are assigned to vibrations of CO bound to
reduced Ru δ+ -sites and indicate dissociative chemisorption of CO 2 . Original figures are provided
by M. Kauer.
ration (1d). The formation of defect B, namely missing Ru-paddlewheels, is accompanied
by lowering the abundance of Ru 2+ and Ru δ+ metal centers in the framework, which

Chapter 4 89
explains the observed changes of the decreased intensity of Ru 2+ and Ru δ+ in the sample
1d.
In our earlier report on pydc-doped Ru-DEMOFs, we communicated on the low
temperature CO2→CO dissociative chemisorption under UHV conditions in a dark
environment, a feature which is not inherent for the parent Ru-MOF. [138] We concluded
that the CO2→CO reduction might be triggered by the reduced Ru δ+ -sites and the pyridyl
N-sites in the proximity of the modified Ru-centers at the nodes. In order to confirm these
assumptions further, we have studied the same reaction at Ru-DEMOFs that feature
reduced Ru δ+ -sites. As these sites have been created by the incorporation of the 5-OH-ip
linker in 1a-d, we have selected two representative samples, 1c and 1d, both exhibiting
high 5-OH-ip incorporation but quite different levels of Ru 2+ and Ru δ+ . As shown in Figure
4.25, upon CO2 dosing for both the parent Ru-MOF and Ru-DEMOFs 1c, an intense and
broad IR band appears at 2336 cm -1 that is assigned to the asymmetric stretching mode
νas(CO2) of physisorbed CO2 binding linearly at various Ru-sites. [198] The weak band at
2273 cm -1 indicates the presence of a minority CO2 species originating probably from the
adsorption of a small amount of 13 CO2 with an expected isotopic shift of 1.03. Apart from
the CO2-related bands, two other bands at 2041 cm -1 and 1993 cm -1 have been observed
in 1c, that are assigned to vibrations of CO bound to the reduced Ru δ+ -sites, matching our
previous data on pydc-doped Ru-DEMOF. [138] This result indicates dissociative
chemisorption of CO2 to CO (reduction) in Ru-DEMOF with 5-OH-ip DL (1c), whereas the
parent Ru-MOF is essentially inactive. However, in comparison to the extremely high
reactivity of pydc-doped Ru-DEMOFs, in which CO2 is nearly totally converted to CO at
higher concentrations of pydc defective linker (e.g. 30%), [138] the production of CO is
rather limited for 5-OH-ip doped Ru-DEMOFs (Figure 4.25). Interestingly, Ru-DEMOF 1d,
is almost inactive for CO2 dissociation. We correlate this observation to the much less Ru δ+
and in turn to the more significant formation of missing node defects (type B) for 1d as
compared to 1c. Overall, the presented IR data demonstrate that the 5-OH-ip doped Ru-
DEMOF samples show much less reactivity for CO2 activation as compared to pydc doped
samples. This cannot be attributed only to the relatively low concentration of reduced
Ru δ+ . In previous study it was suggested that the CO2 activation being promoted by pydc
linker due to the presence of basic pyridyl N sites in proximity to the reactive Ru δ+ . [138]
This hypothesis is indirectly supported by the properties of samples 1c and 1d.

90 Chapter 4
Table 4.5. Possible defect combinations in the prepared Ru-DEMOFs according to the conducted
XANES, UHV-IR and XPS studies.
DL Sample Assumption I Assumption II
1a defectsA* + B defects A*
5-OH-ip
1c defects A*** + B defects A***
1d defects A* + B defects A* + B
ip
2a
2b
defects B
defects B
3a defects A** + B defects A**
5-NH 2 -ip
3b defects A*** + B defects A***
3c defects A* + B defects A* + B
5-Br-ip 4a defects A + B defects A
* expresses relative defects concentration.
Figure 4.26. Other possible defect fragments in the structure of Ru-DEMOFs. a). Two DLs and two
BTC in a fragment of modified paddlewheel b). Two DLs and two HBTC in a fragment of missing
node. Free carboxylates of HBTC were bound with each other via hydrogen bounds. c). Correlated
modified paddlewheel and missing paddlewheel.
The combined spectroscopic characterization data (XANES, XPS, UHV-FTIR with CO and
CO2 as probes) presented above suggest more or less consistent, but complicated picture
on the abundance of the two kinds of defects. Overall, we assume both types A and B being
simultaneously generated in the Ru-DEMOFs in the case of coordinative weakly binding
ligator-sites at the fragmented linkers. Type A appears to be favored at low incorporation
levels, e.g. 1a (8%) and becomes more abundant up to a certain threshold, e.g. 1c (32%).
Along with a further increase of incorporation level, e.g. 1d (37%), defects of type B

Chapter 4 91
appear to dominate over type A. One should be aware that the possibility of formation and
distribution of various defect types is rather diverse and may not be restrict to those
mentioned here. The arrangement of the two defect types in Ru-DEMOFs (1a, 1c and 1d)
is rather diverse. Still, based on the information on XANES and UHV-IR with CO probing,
we can assume two possibilities:
i) both defects of type A and B might be generated in the Ru-DEMOFs (1a-1d) with the
incorporation of 5-OH-ip. The defects of type A are much more competitive and became
gradually dominant in case of the lower doping (samples 1a (8%) and 1c (32%)). Along
with increase of doping level (1d, 37%) of 5-OH-ip, the dominant effect of defects A is
substituted slowly by the defects B;
ii) the defects of type A are generated and becomes gradually dominant in case of
relatively low doping (samples 1a and 1c). Afterwards, defects B are created
simultaneously when the doping level reaches 37% in case of 1d. Therefore, the influence
caused by the defects A could be partly eliminated. Nevertheless, both assumptions
indicate that the defects A play a major role in Ru-DEMOFs 1c (32% of 5-OH-ip). A
comprehensive table summarizing possible defect combinations in the particular Ru-
DEMOFs (based on the performed analyses) is given in Table 4.5 and Figure 4.26.
Additional characterization and quantitative determination of the defect types requires
additional work and support by theoretical modeling.
4.2.4 CO2, CO and H2 sorption properties of Ru-DEMOFs
The previous characterizations suggest the existence of two types of defects (A and B)
being present in the samples in different absolute and relative amounts as a consequence
of the 5-X-ip framework incorporation. Both are likely to influence the gas sorption
properties of the Ru-DEMOFs. Hence, we studied the adsorption of CO2, CO and H2 at range
of samples. In general, the results obtained and discussed in the following are not very
conclusive as the observed changes in gas uptake as a function of DL incorporation are
small or even close to the error of the measurements. Nevertheless, we present the data
and provide a tentative discussion with respect to the possible counter acting effects of
the two types of defects in the samples.

CO 2
adsorbed, mmol/g
92 Chapter 4
3
parent Ru-MOF
1a
1c
1d
2
1
0
0 200 400 600 800 1000
P, mbar
Figure 4.27. CO 2 isotherms collected at 298 K for the parent Ru-MOF and DEMOF derivatives 1a
(8%), 1c (32%) and 1d (37%) with 5-OH-ip DL. Black circles – parent Ru-MOF; blue triangles –
1a; magenta squares – 1c; dark yellow stars – 1d.
CO2 adsorption isotherms (298 K) of the parent reference Ru-MOF sample and 1a and 1c
display a gradual enhancement of the adsorption capacity in the order Ru-MOF < 1a < 1c
along with rising incorporation degree of DL (Figure 4.27). However, the CO2 uptake of
the sample 1d revealed to be 2.9 mmol/g at 1 bar, and lies within the order Ru-MOF < 1d
< 1c (Table 4.6). According to our studies on different defects in the series 1a-1d, these
results are not unexpected. The increase of the CO2 uptake is attributed to the reduced Rusites
at the type A defects and somewhat lowered uptake of 1d is attributed to less
abundant Ru-sites as a consequence of missing metal-nodes (i.e., type B defects). Hence,
higher incorporation level of DL in the sample 1d does not promote the increase of the
CO2 uptake.

CO uptake, mmol/g
Chapter 4 93
Table 4.6. H 2 (77 K) and CO 2 (298 K) uptakes for the parent Ru-MOF and its defect-engineered
variants 1a, 1c, 1d, 2a, 2b, 3a-3c and 4a at 1000 mbar. 1: DL is 5-OH-ip; 2: DL is ip; 3: DL is 5-
NH 2 -ip; 4: DL is 5-Br-ip.
Sample name CO 2 uptake (mmol/g) H 2 uptake (mmol/g)
Parent Ru-MOF 2.7 6.8
1a 3.2 9.6
1c 3.4 8.9
1d 2.9 7.6
2a 3.0 7.4
2b 2.8 6.7
3a 3.4 8.3
3b 3.2 7.8
3c 2.9 7.4
4a 2.6 7.1
2.5
2.0
parent Ru-MOF
1a
1c
1.5
1.0
0.5
0.0
0 200 400 600 800 1000
P, mbar
Figure 4.28. CO isotherms measured at 298 K for the parent Ru-MOF and Ru-DEMOF samples 1a
(8%) and 1c (32%) with 5-OH-ip DL. Black circle – parent Ru-MOF; blue triangles – 1a; magenta
squares – 1c.

H 2
adsorbed, mmol/g
94 Chapter 4
Furthermore, CO adsorption of the parent Ru-MOF, 1a and 1c at 298 K also illustrates the
tendency of enhanced uptake in case of the Ru-DEMOF samples (Figure 4.28). The small
difference between the sample 1a and the parent Ru-MOF on CO adsorption is attributed
to the low incorporation degree of the 5-OH-ip DL (8%). Along with the increase of the DL
incorporation (such as in 1c), the CO uptake rises even at very low pressure (ca. 4 mbar).
This increase of the CO capacity of the Ru-DEMOF is probably due to the generation of the
modified paddlewheels of type A, which expose more open sites as one carboxylate
ligator-site of BTC is substituted by the hydroxyl-group of 5-OH-ip. Besides, the average
electronic density is varied as the oxidation state of ruthenium at the CUS is changed. Both
could contribute to the enhancement of the adsorption properties.
10
8
6
4
2
parent Ru-MOF
1a
1c
0
200 400 600 800 1000
P, mbar
Figure 4.29. H 2 isotherms measured at 77 K for the parent Ru-MOF and DEMOFs 1a (8%) and 1c
(32%) with 5-OH-ip DL. Black circles – parent Ru-MOF; blue triangles – 1a; magenta squares – 1c.
The H2 adsorption isotherms (at 77 K) of the parent Ru-MOF and the Ru-DEMOFs 1a and
1c follow nearly the same trend as in case of CO2 and CO adsorption (Figure 4.29). Both
defect-engineered materials 1a and 1c exhibit higher H2 uptake at 1 bar than the parent
intact framework. In fact, there should be two main kinds of adsorption sites in the Ru-

-Q st
, kJ/mol
Chapter 4 95
DEMOFs (1a and 1c): 1) strong binding affinity between Ru-CUSs and hydrogen, namely
Ru 2+/3+ -sites in the regular paddlewheel units and the Ru δ+ -sites in the modified
paddlewheels (in defects A); 2) the relatively weaker interactions (ie. physisorption and
van der Waals induced interactions) between the hydrogen and ligands/pores walls in the
framework. Obviously, due to the lack of Ru δ+ -sites in the parent Ru-MOF, the Ru-DEMOFs
exhibit higher H2 uptake than the parent Ru-MOF. To quantitatively understand the H2
binding affinity of these samples, the isosteric heats of H2 adsorption (–Qst) was calculated
and reveal an order with 1c > 1a > parent Ru-MOF when comparing the respective values
at 1 mmol (H2) / Ru2-paddlewheel (what might be considered as the saturation
adsorption of H2 at the regular paddlewheel) (Figure 4.30). This suggests stronger binding
affinity of H2 for Ru-DEMOF with 32% of incorporated 5-OH-ip (sample 1c), which again
is attributed to the relative higher amount of Ru δ+ -sites in 1c.
8 parent Ru-MOF
1a
1c
7
6
5
0.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
H 2
adsorbed, mmol/Ru 2
pw
Figure 4.30. Isosteric heats of adsorption of 1a and 1c calculated from the H 2 adsorption
isotherms at 77K and 87K. The vertical line stands for the position where one H 2 molecule is
absorbed per Ru 2 -paddlewheel.

CO 2
adsorbed, mmol/g
96 Chapter 4
Moving further to the 5-NH2-ip DL, respective Ru-DEMOFs (3a-3c) display the same
tendencies in their absorption behavior of CO2 and H2 as in their SBET (N2). From the results
of the XANES studies, we have already revealed that defects B are likely to be generated
at lower doping levels 3a-c (5-NH2-ip) as compared to the samples 1a-d (5-OH-ip). This
difference in defect A/B abundance leads to variation of the CO2 and H2 adsorption in case
of the 3a-c series. Even though 3a-c display higher uptake of CO2 and H2 than the parent
Ru-MOF, the uptake of CO2 and H2 does not further increase after the feeding level of 5-
NH2-ip is raised above 10% (3a) (Figures 4.31 and 4.32). Similar to 1d, we assign the
decrease of the uptake of CO2 and H2 at 1 bar observed for 3c as compared with 3a-b to
more abundant type B defects.
3
parent Ru-MOF
3a
3b
3c
2
1
0
0 200 400 600 800 1000
P, mbar
Figure 4.31. CO 2 isotherms collected at 298 K for the parent Ru-MOF and its derivatives 3a, 3b
and 3c with 5-NH 2 -ip DL. Black circles – parent Ru-MOF; blue triangles – 3a; dark cyan diamonds
– 3b; magenta squares – 3c.

CO 2
adsorbed, mmol/g
H 2
adsorbed, mmol/g
Chapter 4 97
8
6
4
2
parent Ru-MOF
3a
3b
3c
0
0 200 400 600 800 1000
P, mbar
Figure 4.32. H 2 isotherms collected at 77 K for the parent Ru-MOF and its derivatives 3a, 3b and
3c with 5-NH 2 -ip DL. Black circles – parent Ru-MOF; blue triangles – 3a; dark cyan diamonds – 3b;
magenta squares – 3c.
3.0
2.5
2.0
parent Ru-MOF
4a
1.5
1.0
0.5
0.0
0 200 400 600 800 1000
P, mbar
Figure 4.33. CO 2 isotherms measured at 298 K for the parent Ru-MOF and Ru-DEMOF 4a (17%)
with 5-Br-ip DL. Black circles – parent Ru-MOF; blue triangles – 4a.

H 2
adsorbed, mmol/g
98 Chapter 4
8
6
4
2
parent Ru-MOF
4a
0
0 200 400 600 800 1000
P, mbar
Figure 4.34. H 2 isotherms measured at 77 K for the parent Ru-MOF and Ru-DEMOF 4a (17%) with
5-Br-ip DL. Black circles – parent Ru-MOF; blue triangles – 4a.
Another indication of the suggested counter acting effects of the defect sites is the
comparison of the CO2 and H2 uptakes at 2a, 2b and 4a with the parent Ru-MOF (Figures
4.33, 4.34, 4.35 and 4.36). However, the variations are too small to be regarded as
significant. Still, some assumptions can be concluded, which afford us some ideas on the
future design of DEMOFs towards considerable optimization of sorption properties. In
spite of the creation of defects A with Ru δ+ -sites, the rather small change of the H2 and CO2
uptake in the sample of 4a (17% 5-Br-ip) might be contributed to the functional –Brgroups
from the 5-Br-ip linker at the defect-sites. One the one hand, they may create larger
steric hindrances (compared to the other DLs used) blocking, thus, the access for the gas
molecules in spite of the modified paddlewheels with more rooms around Ru-sites. On the
other hand, weaker H2 binding affinity has been found in MOFs composed of ligands with
electron-withdrawing groups. [229-230] Although this influence caused from the interaction
between H2 and ligands is smaller in comparison with the strong one of H2-M sites, it can
be one reason of the observation study in the sample 4a.

CO 2
adsorbed, mmol/g
Chapter 4 99
3.5
3.0
2.5
parent Ru-MOF
2a
2b
2.0
1.5
1.0
0.5
0.0
0 200 400 600 800 1000
P, mbar
Figure 4.35. CO 2 isotherms collected at 298 K for the parent Ru-MOF and DEMOF derivatives 2a
(15%) and 2b (28%) with ip DL. Black circles – parent Ru-MOF; blue triangles – 2a; dark cyan
diamonds – 2b.
The CO2 and H2 adsorption isotherms of 2a and 2b show that 2a exhibits higher uptake.
The adsorption capacity of the sample 2b revealed to be a little lower compared to 2a
while it is still the same as with the parent Ru-MOF (Figures 4.35 and 4.36). Although the
defects B in the Ru-DEMOFs 2a and 2b do not induce ruthenium reduction, vacant-sites
caused from the creation of defects B (missing of Ru-paddlewheels) could still
accommodate gas molecules. In addition, the vacant-sites in the defects B make the gas
molecules access to the surrounding CUS easier. This could be the positive effect of the
defects B in the Ru-DEMOFs with ip DL. On the other hand, the generation of defects B
leads to the partial missing of the di-ruthenium PW units and, hence, the overall CUSs in
Ru-DEMOFs decrease. In the case of Ru-DEMOF 2a, the positive effect of the defects B is
rather dominant and results in the higher H2 and CO2 capacity. But when it comes to 2b,
the negative effect of the defects B eliminates the positive influence on the gas uptake,
which leads to the observation we see in Figures 4.35 and 4.36. The Ru-DEMOFs 1a and
1c featuring higher gas (H2 and CO2) uptake in comparison with 2a (Table 4.6), implying

H 2
adsorbed, mmol/g
100 Chapter 4
that the enhancement of sorption of small molecules (CO2 and H2) attributed to defects A
is stronger than the influence caused from defects B.
8
6
4
2
parent Ru-MOF
2a
2b
0
0 200 400 600 800 1000
P, mbar
Figure 4.36. H 2 isotherms measured at 77 K for the parent Ru-MOF and its derivatives 2a (15%)
and 2b (28%) with ip DL. Black circles – parent Ru-MOF; blue triangles – 2a; dark cyan diamonds
– 2b.
4.2.5 Catalytic test reactions
Ethylene dimerization utilizing MOF supported catalysts has recently attracted a lot of
attention due to its modifiable characteristic under molecular level. [231-234] Most of the
reported MOF catalysts bear isolated single-metal (e.g., Ni, Ir) active-sites. Ru-MOF
materials as heterogeneous catalysts for the ethylene dimerization have not been studied
yet, although chemisorbed Ru-complex on de-aluminated zeolite Y and Ru-complex itself
catalyzing ethylene to butene have been already reported. [235-237] It is known that the
redox activity of Rh in RhCa-X Zeolite plays an important role on catalyzing ethylene
dimerization. [238] Having distinct Ru-CUS available in the Ru-DEMOFs (i.e., different Ru n+ -
species being potentially involved into the redox-process(es) of the reaction flow),

Chapter 4 101
samples 1a (8% of 5-OH-ip) and 1c (32% of 5-OH-ip) have been selected for testing them
as catalysts for ethylene dimerization. In addition, parent Ru-MOF has been used as a
reference. Thus, activated Ru-DEMOFs were loaded into a reactor to catalyze ethylene
Table 4.7. The conversion of ethylene to butene in toluene under different conditions.
Entry Catalyst (mg) Temperature ( °C) Time (h) Additive TOF (h -1 )
1 1c (2.5) 80 24 ---- 0.92
2 1c (2) 80 1 Et 2 AlCl 4.38
3 1c (2) 80 1 ---- 0.88
4 1c (2.4) 26 2 Et 2 AlCl 2.15
5 1c (2.1) 80 2 Et 2 AlCl 4.36
6 1a (2) 80 2 Et 2 AlCl 2.3
7 Parent Ru-MOF (1.8) 80 2 Et 2 AlCl 2.05
dimerization in toluene at different temperatures under the pressure of 800 psi (≈ 55 bar).
In general, all reactions led to the formation of butene without producing any other α-
olefins (Tables 4.7). Addition of Et2AlCl as co-catalyst accelerates the conversion (Table
4.7, entry 2 vs. entry 3). When the reaction has been conducted at 26 °C, lower yield has
been obtained compared to those at 80 °C (Table 4.7, entry 4 vs. entry 5). However,
reactions conducted for 1 h and 24 h give almost the same TOF (0.88 vs. 0.92 h -1 ),
suggesting that the Ru-DEMOF 1c does not suffer the deactivation as a function of onstream
time. Therefore, parent Ru-MOF and Ru-DEMOFs 1a and 1c have been employed
to study the dimerization of ethylene in toluene under optimized condition (800 psi, 80
°C, 2 h) in the presence of Et2AlCl. The obtained product was analyzed by gas
chromatography. As it can be seen from entry 5-7 in Table 4.7 and Figure 4.37, the TOF
value of 1a and 1c increase along with increase of the incorporation level of DL in
comparison with the parent Ru-MOF. Since the contents of the reduced Ru δ+ -sites in 1c is
the highest among the 1a-d series (according to our study above), there should be more
M-CUSs in 1c and therefore it affords the chance to enhance the catalytic activity in the
reaction. Indeed, the transformation of ethylene to butene is the highest (TOF = 4.36 h -1 )
when employing 1c as a catalyst. This value is still much lower than that using zeolite
supported Ru-complex catalysts in the presence of H2 (4.36 vs. 216 h -1 ). However, it is
higher than the TOF value (1 × 10-4 s -1 = 0.36 h -1 ) in the reported reaction without the

102 Chapter 4
presence of H2. [236] Distinction between butene isomers, optimization of the reaction
conditions using Ru-DEMOF materials (such as usage of H2) as well as clarifying the
mechanism of this reaction are outside the scope of this thesis. Nevertheless, the
preliminary results give a rather clear hint that obtained Ru-materials could be utilized as
catalyst for the dimerization of ethylene. Due to the diverse modification of MOF materials
themselves, our current investigations on the ethylene dimerization using Ru-DEMOFs
can afford a platform for further studies on MOFs as catalysts in this field.
Figure 4.37. The tendency of TOF value for parent Ru-MOF and Ru-DEMOF samples 1a and 1c
utilized as catalysts for transformation of ethylene into toluene (800 psi, 80 °C, 2h) in the presence
of Et 2 AlCl (0.81 ml, 1M in heptane). TOF (turnover frequency) = mol product / (mol Metal
(catalyst)*h).
Paal-Knorr pyrrole synthesis has attracted great attention due to the huge synthetic
variety of pyrroles and their derivatives, which are key intermediates for various
pharmaceutical drugs. [239-240] The reaction is typically performed under protic or Lewis
acidic conditions, [241-243] using primary amines and diketones. Ruthenium complex as
catalysts for pyrrole synthesis was rather rare, [244] where the usage of formate salts such
as sodium formate as activators is required. Due to the ability of MOFs on tuning the pore
size and modifying the diverse structure, MOFs have explored to be as catalysts on various
reaction. [29] Phan et al. reported IRMOF-3 as heterogeneous catalyst for the Paal–Knorr

Chapter 4 103
reaction of benzyl amine with 2,5-hexanedione, where it was mentioned that the catalytic
sites might be related to the structure defects. As we know from earlier reports, parent
Ru-MOF ([Ru3(BTC)2Y1.5]n) is constructed from Ru2-paddlewheels, in which the axial Rupositions
are partly occupied by strongly binding Y or by other weakly guest molecules.
After thermal treatment, a fraction of the axial positions can be exposed as open Lewis
acidic sites (useful as catalytic site, for instance). With regard to the structure of the Ru-
DEMOFs discussed in this contribution, two kinds of defects are present. The modified
paddlewheel units (defects A) could provide the materials with additional sites around
the partly reduced Ru-centers. On the other hand, the eliminated entire Ru-paddlewheel
clusters (defects B) can form vacant-sites to play a role on affecting the adsorption
properties, especially when the functional X-group at the defect generating linker is as
small as H. Hence, Ru-DEMOFs 1a-1c, 2a and 2b have been utilized for catalyzing the
reaction of 2,5-hexadione and aniline in toluene at 90 °C to form dimethyl-phenyl-1Hpyrrole
(Scheme 4.1).
Scheme 4.1. Scheme of the Paal-Knorr reaction.
It is interesting to note that all of the selected Ru-DEMOFs show apparently enhanced
conversion of aniline to the pyrrole within the initial 4 hours in comparison with the
parent Ru-MOF (Figure 4.38). Among the used materials, Ru-DEMOFs 1a and 2a exhibit
the highest catalytic activity, although the other Ru-DEMOFs (1b, 1c, 1d and 2b)
incorporate more DL (Table 4.8). The steric hindrances and distinct defect types (A vs. B)
could be the main reason of this phenomenon. When Ru-DEMOF samples with 5-OH-ip DL
(1a-d) were employed as catalysts, the yield of pyrrole has been increased from 48%
(using parent Ru-MOF as the catalyst) to 58% (1d), 65% (1c), 73% (1b) and 77% (1a),
respectively. This is assigned to the presence of the reduced Ru-centers (defects A) in
these materials. Reduced, softer binding Ru δ+ -sites can be more easily coordinated to the
O atom of the carbonyl group, which favors the nucleophilic attack from the lone-pair of
the amino group of aniline. However, when the incorporation of 5-OH-ip increases, the
gradual dominance of the defects B in these materials probably eliminates part of the

104 Chapter 4
reactive metal centers, thus, affecting the catalytic activity of the 1b-d samples. On the
other hand, Ru-DEMOF 2a displays higher yield of pyrrole compared to the parent Ru-
MOF (82% vs. 48%), regardless of the partial absence of the metal centers (defects B)
(Figure 4.39). This could be a result of the smaller steric hindrance surrounding the Ru-
CUSs while employing the H2ip DL. When the contents of the incorporated DLs are rather
small (i.e., as in 2a), the negative influence caused by missing metal centers is relatively
insignificant compared with the positive effect of the smaller steric hindrance. Therefore,
2a Ru-MOF material shows as high catalytic activity in present reaction as 1a. Similar
observations have been found for the samples 1b-c because of the somewhat larger steric
hindrance of OH-groups in spite of the type A defect in these materials. To note, using
IRMOF-3 as catalysts in the same reaction, 96% conversion after 60 min was achieved.
However, this could be attributed to the higher regent ratio (aniline: 2,5-hexanedione =
1:1.7). [245] Nevertheless, the current study using Ru-DEMOFs as catalysts give us insight
into the influence of catalytic activity caused by different defect types. For further
investigation, it would also be interesting to optimize the catalytic activity by improving
the regent ratio.
Figure 4.38. Time-yield plot of Paal-Knorr synthesis of aniline reacting with 2,5-hexadione, giving
the pyrrole employing Ru-DEMOFs 1a-1d (with 8%, 20%, 32% and 37% 5-OH-ip incorporation,
respectively) as catalysts in comparison with the parent Ru-MOF(parent). Blank stands for the
experiment where no catalyst was added into the reaction mixture.

Yield, %
Chapter 4 105
Table 4.8. Comparison of the yields of pyrrole and TOF values after 4 h in the Paal-Knorr reaction
for different Ru-DEMOF samples as well as the parent Ru-MOF (used as a reference).
Sample Ru content (mol %) yield at 4h, % TOF(h -1 )*
Parent Ru-MOF 2 48 6.17
1a 2 77 9.83
1b 2 73 9.25
1c 2 65 8.17
1d 2 58 7.25
2a 2 82 10.36
2b 2 57 7.09
blank - 28 -
* TOF value was calculated by mol of product (mol of Ru) -1 h -1 .
100
80
60
40
20
2a
2b
parent Ru-MOF
blank
0
0 4 8 12 16 20 24
Time, h
Figure 4.39. Time-yield plot of Paal-Knorr synthesis of aniline reacting with 2,5-hexadione, giving
the pyrrol using Ru-DEMOFs 2a (15% ip incorporation) and 2b (28% ip incorporation) as
catalysts in comparison with the parent Ru-MOF. Blank stands for the experiment where on
catalyst was added into the reaction mixture.

106 Chapter 4
4.2.6 Conclusions
Applying the solid solution approach, a range of Ru-DEMOFs ([Ru3(BTC)2-x(5-X-ip)xYy]n)
isostructural to HKUST-1 were obtained with the framework incorporated DLs 5-OH-ip
(1a-d), ip (2a and 2b), 5-NH2-ip (3a-c) and 5-Br-ip (4a)). Comparably high SBET have been
measured for Ru-DEMOF samples (947-1302 m 2 /g) when considering the parent Ru-MOF
material [Ru3(BTC)2Y1.5]n (704-998 m 2 /g). [82, 208] The highest level of DL incorporation
appeared to be 37% (1d, 5-OH-ip). The data are consistent with two kinds of defects (A
and B) being introduced to the Ru-DEMOFs depending on the nature of the functional
groups (X) of the DLs 5-X-ip (see Figure 4.5). DLs with steric less demanding X-groups of
probably still existing, but weaker coordinative binding properties as a carboxylate ligator
are likely to favor type A defects, defined as modified paddlewheel nodes exhibiting
reduced Ru δ+ -sites. Along with the increasing of the DL contents, defects of type B, i.e.
missing node defects, can be created simultaneously in the DEMOFs. When the functional
groups in the DL 5-X-ip are much smaller than carboxylate and non-coordinating X (such
as H), the defects of type B, defined as missing node defects, apparently become more
dominant even in case of low doping level (case of 2a and 2b). The more or less
simultaneous presence of two kinds of defects leads to the synergetic and as well
counteracting effects on the porosity, sorption and catalytic properties. In fact, Ru-DEMOF
1c (32% 5-OH-ip incorporation), in which defects of type A are more dominant, reveals
the highest BET surface area (1302 m 2 /g) among the all samples, including parent Ru-
MOF and its DEMOF derivatives reported so far. [138] Concerning the enhanced gas sorption
properties, type A defects are more important than those effects related to the defects of
type B, as reduced and more accessible Ru δ+ -sites have been produced in defect type A.
When it comes to the catalytic activity, Ru δ+ -sites in Ru-DEMOF 1c are suggested to be
responsible for the significant increase of TOF value of ethylene dimerization, as clearly
seen while comparing with the parent Ru-MOF and 1a, in which no or less Ru δ+ -sites are
present. However, in case of Paal-Knorr pyrrole reaction, the possible steric hindrance
between the functional groups (OH) at the DL and 2,5-hexadione substrate is suggested
to be responsible for the reduced activity of the Ru-DEMOFs 1a-d, although they all
feature enhanced conversion compared with the parent Ru-MOF. All in all, the described
Ru-DEMOFs obtained via solid solution approach employing various DLs turned out to be
rather complex materials to be studied and characterized. Nevertheless, the observed
spectroscopic evidences as well as effects on sorption properties and catalytic

Chapter 4 107
performance reasonably fit into a model of the two types of defects, modified and missing
nodes (see Figure 4.5), respectively.

108 Chapter 4
4.3 Defects Engineering in [Cu3(BTC)2]n: Effect of the synthetic parameters
To date, the introduction of defects into the [M3(BTC)2]n structure has been achieved via
mixed-linker solid solutions approach for frameworks where M = Cu or Ru. [136, 138-140] By
varying the DLs, simultaneously mixed with H3BTC during the synthesis, DEMOFs with a
general formula [M3(BTC)2-x(DL)x]n could be obtained. Interestingly, in spite of the very
similar structural long range order of the DEMOFs, local point defects can influence the
metal environment at the PW and also enhance structural properties such as porosity.
Different types of defect A and B in Ru-DEMOFs as well as their influence on the sorption
and catalytic properties have already been described in Chapter 4.2. More interestingly,
incorporation of pydc into [M3(BTC)2]n, the generation of reduced metal sites was found
in both the formed Ru-DEMOFs ([Ru3(BTC)2-x(pydc)xYy]n) [138] and Cu-DEMOFs
([Cu3(BTC)2-x(pydc)x]n) [139] However, only in the former case, CO2 → CO dissociative
chemisorption (“reduction”) at low temperature (90 K) under UHV conditions was
achieved. Utilizing 5-OH-ip as DL during the MOF synthesis, the mesopores prefer to be
generated in Cu-DEMOFs rather than in Ru-DEMOFs. Moreover, even the modification of
the doping level of the same DL in Cu-DEMOF can control the formation of the framework
with micropores or mesopores. [139] Recently, Hupp et al. reported the formation of
missing Cu 2+ node defects in the obtained Cu-DEMOF with ip incorporation, [140] while
defect type A (modified PW units) related Cu + formation was observed in the Cu-DEMOF
with pydc or other 5-X-ip(X = OH, CN, NO2) incorporation. [139] With regard to these
accounts, it is essential to understand the structural complexity of DEMOFs, which will be
beneficial to tailor their advanced properties. Therefore, in comparison with rather
complicated Ru-(DE)MOFs system and following the description of Cu-DEMOFs reported
by Hupp et al. and Fang et al., the relative simple [Cu3(BTC)2]n has been chosen as a
candidate here to be incorporated by ip DL under different synthetic conditions (e.g.
solvent, nature of the metal salts). Systematically study on the formation of M-DEMOFs
variants of [M3(BTC)2]n structure, namely, types of local defects (i.e. the generation of
reduced metal-sites or not), their origin as well as the dependence on variation of the
synthetic conditions will be investigated.

Intensity, a. u.
Chapter 4 109
4.3.1 Preparation and characterization of Cu-DEMOF samples [Cu3(BTC)2-x(ip)x]n
All samples D1-8 have been prepared via mixed-linker soild solution approach with
distinct relative H3BTC : H2ip molar ratios under solvothermal conditions (80 °C, 20 h).
For each sample, various Cu-salts and solvents (DMF or EtOH) have been employed.
Samples D5 and D6 are prepared following reported method. [140]
4.3.1.1 Solids obtained using Cu(BF4)2∙6H2O as metal precursor
D4
D3
D2
D1
Cu-BTC_sim.
5 10 15 20 25 30
2, degree
Figure 4.40. PXRD patterns of the activated Cu-DEMOF samples D1-4 in comparison with the
patterns simulated from the single-crystal XRD data of the reported [Cu 3 (BTC) 2 ] n (Cu-BTC_sim).
Metal source: Cu(BF 4 ) 2 6H 2 O. Solvent used for synthesis of D1 and D2 (blue patterns): DMF; for
D3 and D4 (red patterns): EtOH.
PXRD patterns of all activated samples D1-4 (Figure 4.40) match well with the simulated
patterns of [Cu3(BTC)2]n (Cu-BTC_sim), suggesting that they all are all phase-pure,
crystalline and isostructural with the non-doped parent Cu-BTC. To note, the small double
reflection of the as-synthesized sample D4_as at around 9.4°and reflections at 5.7°for the

Intensity, a. u.
110 Chapter 4
as-synthesized samples D2-D4_as (Figure 4.41) disappear after samples activation (i.e.
heating under vacuum). Thus, the origin of these reflections might come from coordinated
solvent molecules, which under employed activation conditions are subsequently
removed. FT-IR spectra of all activated Cu-DEMOFs samples do not vary from the FT-IR
spectrum of the parent Cu-BTC, displaying also overlapping of the characteristic bands of
ip and BTC (Figure 4.42). However, the typical νs(COO) and νas(COO) bands of
carboxylates are observed at around 1442 cm -1 and 1366 cm -1 , respectively. Moreover, the
absence of [BF4] - (from the used Cu-salts) is confirmed, as no ν(B–F) band was found at
1073 cm –1 . [208]
D4_as
D3_as
D2_as
D1_as
Cu-BTC_sim.
5 10 15 20 25 30
2, degree
Figure 4.41. PXRD patterns of the as-synthesized Cu-DEMOF samples D1-4_as in comparison
with the patterns simulated from the single-crystal XRD data of the reported [Cu 3 (BTC) 2 ] n (Cu-
BTC_sim). Metal source: Cu(BF 4 ) 2 6H 2 O. Solvent used for synthesis of D1 and D2 (blue patterns):
DMF; for D3 and D4 (red patterns): EtOH.

Chapter 4 111
H 3
BTC
H 2
ip
D4
D3
D2
D1
Cu-BTC
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm -1
H 3
BTC
H 2
ip
D4
D3
D2
D1
Cu-BTC
2000 1500 1000 500
wavenumber, cm -1
Figure 4.42. IR spectra of the activated samples D1-D4 in comparison with the spectra of the
parent Cu-BTC, H 3 BTC and H 2 ip. Bottom figure represents selected region from 2000 cm -1 to 350
cm -1 . Metal source: Cu(BF 4 ) 2 6H 2 O. Solvent used for synthesis of the D1 and D2 (blue): DMF; for
the D3 and D4 (red): EtOH.

weight loss, %
112 Chapter 4
100
Cu-BTC
80
60
D3
40
D1
D2
D4
20
100 200 300 400 500 600
T, C
Figure 4.43. TG curves of the prepared Cu-DEMOFs D1-4 in comparison with the parent Cu-BTC.
Metal source: Cu(BF 4 ) 2 6H 2 O. Solvent used for synthesis of the D1 and D2 (blue): DMF; for the D3
and D4 (red): EtOH.
The thermal stability of the all obtained Cu-DEMOF samples D1-4 (Figure 4.43) is
considerable preserved (decomposition temperature equals ca. 300 °C). A little decrease
of thermal stability in comparison with the parent Cu-BTC (decomposition temperature
is ca. 330 °C) might be attributed to the incorporation of ip DL into the MOF structures,
where formation of the defects at Cu2-PW is expected (Figure 4.5). For example, Cu-COO
bonds can be partially substituted by the weak interactions between benzene ring of ip
and Cu-centers in case of defects of type A (modified paddlewheel). In other case (defects
of type B), missing of complete nodes of the Cu2-PWs is probably to happen as well.
Consequently, presence of such defects (either A, B, or both of them) may cause the slight
decrease of the thermal stability of the final DEMOFs.
4.3.1.2 Cu-DEMOFs obtained using Cu(NO3)2·3H2O as metal precursor
The phase purity and crystallinity of all samples D5-8 have been confirmed by the PXRD
analysis of both as-synthesized and activated solids (Figures 4.44 and 4.45). Besides,

Intensity, a. u.
Intensity, a.u.
Chapter 4 113
D8_as
D7_as
D6_as
D5_as
Cu-BTC_sim.
5 10 15 20 25 30
2, degree
Figure 4.44. PXRD patterns of the as-synthesized Cu-DEMOF samples D5-8_as in comparison
with the patterns simulated from the single-crystal XRD data of the reported [Cu 3 (BTC) 2 ] n (Cu-
BTC_sim). Metal source: Cu(NO 3 ) 2·3H 2 O. Solvent employed for the synthesis of the D5 and D6
(olive patterns): DMF plus HBF 4 ; for D7 and D8 (magenta patterns): only DMF.
D8
D7
D6
D5
Cu-BTC_sim.
5 10 15 20 25
2, degree
Figure 4.45. PXRD patterns of the activated Cu-DEMOF samples D5-8 in comparison with the
patterns simulated from the single-crystal XRD data of the reported [Cu 3 (BTC) 2 ] n (Cu-BTC_sim).
Metal source: Cu(NO 3 ) 2·3H 2 O.

weight loss, %
114 Chapter 4
recorded PXRD patterns are in a good agreement with the patterns simulated from the singlecrystal
XRD data of the reported [Cu 3 (BTC) 2 ] n , suggesting all prepared Cu-MOFs being
isostructural analogs of the parent Cu-BTC. These observations indicate that Cu-DEMOFs with ip
DL incorporation can be prepared employing various Cu-precursors. However, only in the case of
using DMF as a reaction medium, phase-pure solids have been obtained. Similarly, synthesis of the
D7 and D8 in EtOH instead of DMF yielded precipitates with additional unknown phases (Figure
7.23).
Like in the case of Cu-DEMOFs D1-4, IR spectra of the samples (D5-8) obtained from the
reaction of Cu(NO3)2·3H2O and mixed linkers do not differ from the parent Cu-BTC (Figure
4.46). The presence of the residues from the starting metal precursors can be ruled out,
as no bands of [NO3] - (845-815 cm -1 ) is observed in the spectra of the prepared DEMOF
solids, which supports the conclusions made above on their phase purity. TGA curves of
all samples D5-8 show a slight decrease of thermal stability (Figure 4.47), in analogy to
the other four Cu-DEMOFs D1-4 obtained using Cu(BF4)2 6H2O as metal precursor,
suggesting no significant influence of the metal source on the thermal stability of the
resulting DEMOFs.
100
80
D8
Cu-BTC
60
D6
40
D5
D7
20
100 200 300 400 500 600
T, C
Figure 4.46. TG curves of the Cu-DEMOFs D5-8 in comparison with the parent Cu-BTC. Metal
source: Cu(NO 3 ) 2·3H 2 O. Solvent used for preparation of the D5 and D6 (olive): DMF plus HBF 4 ; for
D7 and D8 (magenta): only DMF.

Chapter 4 115
H 3
BTC
H 2
ip
D8
D7
D6
D5
Cu-BTC
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm -1
H 3
BTC
H 2
ip
D8
D7
D6
D5
Cu-BTC
2000 1750 1500 1250 1000 750 500
wavenumber, cm -1
Figure 4.47. IR spectra of the activated samples D5-D8 in comparison with the parent Cu-BTC as
well as used linkers H 3 BTC and H 2 ip. Right figure represents selected region from 2000 cm -1 to
350 cm -1 . Metal source: Cu(NO 3 ) 2·3H 2 O. Solvent used for preparation of the D5 and D6 (olive):
DMF plus HBF 4 ; for D7 and D8 (magenta): only DMF.

116 Chapter 4
4.3.2 Composition and porosity of the prepared Cu-DEMOFs
In order to determine the presence and amount of the framework incorporated DL ip in
the Cu-DEMOF solids, 1 H-NMR spectroscopic measurements have been performed on all
activated samples (which were previously acid-digested). Apart from the resonance at ca.
8.6 ppm, which originates from the aromatic protons of BTC, three additional peaks
appear at ca. 7.6, 8.1 and 8.4 ppm in all Cu-DEMOF samples D1-8 (Figures 7.15-7.22),
which could be attributed to the aromatic protons of ip DL. The ratio of incorporated ip to
the total linkers-amount (BTC+ ip) in the obtained solids have been estimated from the
integrals of the proton resonances in 1 H-NMR spectra and are listed in Table 4.9.
Table 4.9. The incorporation of ip (calculated from the integration of proton-signals in 1 H-NMR
spectra) and BET surface area (estimated from the N 2 sorption experiments (at 77 K)) of the
obtained Cu-DEMOFs.
Samples
Metal source
Synthesis
solvent
Molar ratio of ip : (BTC + ip)
feeding
incorporation
(obtained)
S BET (m 2 /g)
D1 Cu(BF 4 ) 2·6H 2 O DMF 1/2 20% 1833
D2 Cu(BF 4 ) 2·6H 2 O DMF 2/3 25% 2030
D3 Cu(BF 4 ) 2·6H 2 O EtOH 1/2 12% 1931
D4 Cu(BF 4 ) 2·6H 2 O EtOH 2/3 17% 1973
D5 Cu(NO 3 ) 2·3H 2 O DMF+HBF 4 1/2 23%, 28%* 1841, -*
D6 Cu(NO 3 ) 2·3H 2 O DMF+HBF 4 2/3 33%, 33%* 1305, 2030*
D7 Cu(NO 3 ) 2·3H 2 O DMF 1/2 21% 1818
D8 Cu(NO 3 ) 2·3H 2 O DMF 2/3 30% 1673
* reported values in the literature. [140]
On the whole, it might be concluded, that both metal salts that have been tested in present
studies could be successfully utilized to introduce ip DL into Cu-BTC. Curiously, addition
of HBF4 increases the amount of the incorporated ip (in about 2-3%) when Cu(NO3)2·3H2O
is utilized. However, on the basis of the performed quantitative calculations and taking
into account an error of integrals of the 1 H-NMR signals, this difference might be ignored.
Hence, the incorporation amount of ip in the reproduced sample D5 can be also
considered to be same as the reported values (Table 4.9). [140] In the case of usage
Cu(BF4)2·6H2O, the reaction in DMF yields to higher extent of ip incorporation (about 8%

V, cm 3 /g
Chapter 4 117
more) in comparison with syntheses performed in EtOH. Thus, the protic EtOH solvent
probably slows down to a certain degree the BTC↔ip substitution rate. Therefore, it is
not surprising that the above-mentioned samples prepared from Cu(NO3)2·3H2O using
EtOH instead of DMF are not phase-pure solids (Figure 7.23).
600
500
400
300
200
100
/ Cu-BTC
/ D1
/ D2
/ D3
/ D4
0
0.0 0.2 0.4 0.6 0.8 1.0
relative pressure, p/p 0
Figure 4.48. N 2 sorption isotherms collected at 77 K for the Cu-DEMOF samples D1-4 in
comparison with the parent Cu-BTC. Closed and opened symbols represent the adsorption and
desorption isotherms, respectively. Black circles - Cu-BTC; blue triangles - D1; blue stars - D2; red
diamonds - D3; red squares - D4. Metal source: Cu(BF 4 ) 2 ·6H 2 O. Solvent employed for the synthesis
of the D1 and D2 (blue): DMF; for D3 and D4 (red): EtOH.
All N2 sorption isotherms recorded at 77 K for Cu-DEMOFs D1-8 as well as the parent Cu-
BTC show type I isotherms without any hysteresis loop (Figures 4.48, 4.49), suggesting
their microporosity. To recall and opposed to these observations, in the Cu-DEMOFs with
pydc or 5-X-ip DLs (X = NO2, CN, or OH), the generation of mesopores were reported. [139]
This different behavior indicates, that the defects in Cu-DEMOFs prepared in current work
tend to be isolated rather than correlated as in earlier reported homologous frameworks
(Figure 4.17). Interestingly, all Cu-DEMOFs synthesized from Cu(BF4)2·6H2O (D1-4) show

V, cm 3 /g
118 Chapter 4
500
400
300
200
100
/ Cu-BTC
/ D5
/ D6
/ D7
/ D8
0
0.0 0.2 0.4 0.6 0.8 1.0
relative pressure, p/p 0
Figure 4.49. N 2 sorption isotherms collected at 77 K for the Cu-DEMOF samples D5-8 in
comparison with the parent Cu-BTC. Closed and opened symbols represent the adsorption and
desorption isotherms, respectively. Black circles - Cu-BTC; olive triangles - D5; olive stars - D6;
magenta diamonds - D7; magenta squares - D8. Metal source: Cu(NO 3 ) 2 3H 2 O. Solvent utilized for
the synthesis of the D5 and D6 (olive): DMF +HBF 4 ; for D7 and D8 (magenta): DMF.
increased SBET in comparison with the parent Cu-BTC (1561 m 2 /g) (Table 4.9). In fact, the
porosity of these samples rises along with the increase of incorporated amount of ip, no
matter whether DMF or EtOH has been used. Thus, enhanced porosity provides indirect
indications on absence of unreacted H2ip and proves the in-framework incorporation of
ip in these solids. Remarkably, Cu-DEMOF sample D2 (25% of ip incorporation) reveals
the highest SBET (2030 m 2 /g) among all the samples. Furthermore, solids D6, repeated
following communicated earlier method, show a little lower SBET than the reported values
(2030 m 2 /g). [140] Unfortunately, there is no exact reported SBET value for D5. Only a
general increase trend of SBET value along with the incorporation amount of ip was given
in the earlier report. However, in current study, incorporation of higher quantity of ip, as
in the case of sample D6, leads to the decreased porosity instead in comparison with D5.
Similar trend has been traced for the solids D7 and D8, where the latter sample reveals a
little lower SBET value than the former. Consequently, it might be possible that some guest

Chapter 4 119
(e.g. H2ip, H3BTC, etc.) inclusion happens in the case of D6 and D8. Thus, the highest
incorporation degree of ip in Cu-BTC should be around 25% (D2 or D5). Although utilizing
Cu(NO3)2·3H2O as metal-precursor, the samples with the same incorporation level of ip
could be obtained (D5, 23% ip), the usage of nitrate salt results solids with lower porosity.
Attempts to incorporate even more ip most probably would lead to the guest inclusion in
the pores of DEMOFs. Due to less nucleophilic and basic character of “inert” [BF4] - anion
in comparison with [NO3] - , employing Cu(BF4)2·6H2O probably facilitates the selfassembly
between the metal clusters and the linkers during synthesis and could avoid the
guest inclusion
4.3.3 Oxidation state(s) of metal-sites in prepared Cu-DEMOFs
In the earlier report from Hupp and co-workers, the generation of missing Cu 2+ -nodes was
proposed. [140] In order to gain a deeper understanding of the defects generated in Cu-
DEMOFs under different synthetic conditions, D1 and D2 samples, which are synthesized
from different Cu-salts (Cu(BF4)2·6H2O) and feature high porosity as well as distinct
incorporation level of ip, have been chosen as candidates for CO probing monitored by
UHV-IR spectroscopy. It is interesting to investigate if there is any presence of Cu + in the
obtained solids. Thus, the bands observed at 2178 cm -1 for D1 and D2 appear at the same
position as in the spectra of the parent Cu-BTC and correspond to CO bound to Cu 2+ -sites
in the PW through electrostatic and σ-donation interactions (Figure 4.50). [246] Besides,
additional intense bands at 2120 cm -1 due to C-O stretching vibrations that are associated
with Cu + - species are seen in spectra of both D1 and D2. The appearance of Cu + - species
in sample D1 and D2 can origin from several possibilities:
i) “intrinsic” defects in the framework of Cu-BTC and its analogs. It is known that intrinsic
defects can be present to some extent in the MOF solids. [137, 247-249] Especially, intrinsic
defects in HKUST-1 has been described. [249-250] . The activation procedure (i.e. thermal
treatment under vacuum) lead to some decarboxylation and “missing” COO-sites, [249]
therefore, the generation of Cu + was observed. It is possible that during the thermal
treatment of D1 and D2, such intrinsic defects are formed as well.
ii) “intentional” defects

120 Chapter 4
Figure 4.50. From left to right: UHV-IR spectra of the parent Cu-BTC and Cu-DEMOFs D1 (20% of
ip) and D2 (25% of ip) upon CO dosing (p(CO): 1×10 -6 - 3×10 -4 mbar) collected at 92-98 K after
annealing at 480 K. The low intensity absorption bands at 2127 cm -1 in the parent Cu-BTC indicate
some inherent defects that cannot be avoided during the crystal formation. Figure has been
provided by M. Kauer.
As illustrated in Figure 4.5, two representative types of defects are expected in the
formation of DEMOFs. The generation of defect type A (i.e. modified PWs with the creation
of the reduced Cu-sites) can be also expected in the solids D1 and D2 due to the utilization
of reducing agents (DMF). Although Cu + related CO bands (2127 cm -1 ) appear in parent
HKUST-1, the relative intensity to Cu 2+ related CO bands (2178 cm -1 ) is lower. However,
in both D1 and D2 the CO bands at 2120 cm -1 attributed to Cu + -CO interaction turn to be
dominant in comparison with the bands at 2178 cm -1 . Thus it gives us a hint that presence
of defect type A can be one of the possibilities. Notably, intensity of both Cu 2+ - (2178 cm -
1 ) and Cu + -related bands (2120cm -1 ) decreases from D1 (20% ip) to D2 (25%). The
similar scenario has been also found for the 5-OH-ip incorporated Ru-DEMOF samples
described in Chapter 4.2, suggesting thus simultaneous formation of defects B upon higher
doping of DL, namely missing Cu-PWs. Consequently, lower abundance of Cu 2+ and Cu +
metal centers in the D2 frameworks expected, explaining observed changes of the
decreased intensity of the bands related to Cu 2+ and Cu + . Cu-DEMOFs with ip (obtained
also from Cu(NO3)2·3H2O) reported earlier by Hupp et al. suggest generation of only
defects type B by simulation of defects. Thus, it might be possible that anions of the
utilized metal precursors play an important role on intentional defects formation in Cu-

Chapter 4 121
DEMOFs. Moreover, as the generation of only defect type B was observed in Ru-DEMOF
analogs of HKUST-1 with ip DL, the effect from different metal ions (Cu, Ru) on the
formation of intentional defects in M-DEMOFs should also be taken into account.
4.3.4 Conclusions
Adopting Cu(NO3)2∙3H2O and Cu(BF4)2∙6H2O as metal sources and different feeding of
H2ip DL results in crystalline Cu-DEMOFs, which are isostructural analogs of Cu-BTC. All
obtained Cu-DEMOF solids show good thermal stability, which appeared to be not affected
by the employed reactants (i.e. metal salts and solvents). Based on the composition and
porosity, DMF found to be a better reaction solvent than EtOH leading to higher
incorporation degree of ip and higher porosity of the resulting DEMOFs (for the given
feeding). However, when the feeding of ip is increased, the usage of Cu(NO3)2∙3H2O as
precursor should be carefully monitored owing to accompanied effects of guest(s)
inclusion. Nevertheless, current studies demonstrate the highest ip framework
incorporation into Cu-BTC could reach up to 25%.
More importantly, UHV-IR spectra recorded upon CO dosing suggest generation of Cu + in
the prepared Cu-DEMOF samples D1 and D2. Two important caused factors are
concluded: one is related with the intrinsic defects induced by thermal activation and the
other is intentional defects (i.e. modified PWs). In the case of intentional defects, usage of
reducing agents, modifying the metal precursors including the cations and anions could
be the driven force to generate reduced metal-sites. In one word, even in the “simple
looking” HKUST-1 (in comparison with its Ru analogs), the defect-engineering is
complicated and carefully consideration is required for the elaboration.

5 Simultaneous introduction of various palladium active sites
into MOF via one-pot synthesis: Pd@[Cu3-xPdx(BTC)2]n ‡
Abstract
Simultaneous structural incorporation of palladium within Pd-Pd and/or Pd-Cu
paddlewheels as framework-nodes and Pd nanoparticles (NPs) dispersion into MOF have
been achieved for the first time via one-pot synthesis. The substitution of Cu 2+ by Pd 2+
within polymer carcass as well as the loading of Pd NPs have been confirmed in particular
by XPS. Solids featuring such both Pd-sites show enhanced activity (compared to the
parent “Pd-free” Cu-BTC) in the hydrogenation of p-nitrophenol (PNP) to p-aminophenol
(PAP) using NaBH4 as a reducing agent.
‡ Work in this chapter is covered in the manuscript submitted to Dalton Trans.

Chapter 5 123
5.1 Introduction on the selection of metal type in MOFs
High structural and compositional design ability of metal-organic frameworks (MOFs)
and, hence, the ability of tailoring their properties made MOFs to be among the most
topical materials over last decades. Along with linker(s) modification [64, 123, 251] and
guest(s) inclusion, [252-253] variation of the metal center(s) is also a powerful tool to fine
tune MOFs functionalities. In fact, both control over coordinatively unsaturated metal
sites (CUS) (e.g., via “defects-engineering”) [137] and partial metal substitution (e.g., via
mixed-metal “solid solution” approach) could considerably enhance MOFs activity,
especially in catalysis [138, 141, 254] and selective gas sorption/separation. [255-256]
Figure 5.1. Partial metal (Cu vs Mn, Zn, Co) substitution in Cu-BTC. Reprinted with permission
from D. F. Sava Gallis, M. V. Parkes, J. A. Greathouse, X. Zhang and T. M. Nenoff, Chem. Mater., 2015,
27, 2018-2025. Copyright (2015) American Chemical Society. [256]
Combination of distinct metal-ions, which are closely related in coordination chemistry
and have similar effective ionic radii (rion), like Cu 2+ (73 pm) / Zn 2+ (74 pm) couple [257] for
instance, within single MOF has been reported for several structural types. [131, 255, 258] In
fact, partial substitution of Cu 2+ by Zn 2+ and some other metals of 3d-row, namely Co, Fe
and Mn, in HKUST-1 ([Cu3(BTC)2]n, BTC = benzene-1,3,5-tricarboxylate) has been recently
reported (Figure 5.1). [133, 256] Curiously, in later case doping with second metal caused
enhanced selective sorption of O2 vs N2. [256, 259] What is more challenging however, is to
take benefits of solid solution approach to introduce more distinct metals of 4d- [134] or 5drow
[260] as framework-nodes. In particular, metals of the platinum group are highly
attractive as catalytic- / strong sorption-centers. Besides, square planar coordination is

124 Chapter 5
preferred like Cu 2+ . [261-263],[264] Still, due to kinetic reasons, these metal ions are difficult to
be crystallized within 3D structures [263-264] and, therefore, almost neglected in MOF
field. [265] Reports on MOFs featuring Pd-Pd, Pd-M PW nodes could not be even found.
Figure 5.2. (a) Structural and (b) schematic representations of the synthesis of the cuboctahedral
bimetallic MOPs. Reproduced from J. M. Teo, C. J. Coghlan, J. D. Evans, E. Tsivion, M. Head-Gordon,
C. J. Sumby and C. J. Doonan, Chem. Commun., 2016, 52, 276-279, with permission of The Royal
Society of Chemistry. [264]
Recent years the study of Ru-based MOFs has been mainly focused on the synthesis of Ruanalogues
of HKUST-1, which were successfully obtained in our group. [82, 198] Following
the previous studies, in this work the attention was turned also to palladium, which is well
known to facilitate dissociation of molecular hydrogen (spill-over effect). [266-268]
Furthermore, bimetallic Pd/M-paddlewheel (PW) complexes have been lately found to be
promising economical catalysts in the intramolecular benzylic C-H amination. [269]
Interestingly, to date immobilization of Pd-nanoparticles [270-273] and decoration of MOFs
interior with Pd-complexes [274-275] have been investigated a lot. Moreover, porous Pd 2+ -
M 2+ (M = Cu, Ni, Zn) metal-organic polyhedra have been very recently described (Figure
5.2). [264] Regardless obvious interest, studies on integration of palladium as a framework
node into a MOF are, however, in its infancy. [265, 276-277] Hence, considering its structural
peculiarities (i.e., PW SBUs and CUSs) [35] and primary experimentally studies on [Cu3-
xRux(BTC)2]n including Ru 3+ (rion = 68 pm), [257] it would be of interest to choose
[Cu3(BTC)2]n (Cu-BTC) as a matrix for in-framework incorporation of Pd 2+ (rion = 86

Chapter 5 125
pm) [257] via solid solution approach. However, a rigorous exclusion of reducing conditions
during MOF synthesis is difficult. Even technical activation may cause reduction at some
metal sites due to decarboxylation. [250] Therefore, the standard protocol for HKUST-1
synthesis is, intentionally, not changed in this stage.
On the other hand, loading of Pd 0 NPs onto MOF is widely investigated as gas
adsorbents [273, 278-279] and catalysts in hydrogenation, [271-273, 280-281] cross coupling [272, 282]
reaction and so on. [283] To note, one of the most common approaches to obtain Pd 0 @MOFs
is using H2 to reduce Pd 2+ -precursor loading MOFs that are prepared via solution
impregnation by soluble Pd 2+ species. In some cases, trace amount of Pd 2+ can be still
observed after reduction. [282] Actually, according to the concept of post-synthetic metalion
exchange, [117, 121, 284-285] Pd 2+ substitution in the metal nodes of MOFs could probably
happen under this impregnation. Interestingly, the discrimination between the two Pdsites
(from extra-framework loading or in-framework incorporation) is disregarded to
some extent in the current literatures. Given both facts, herein an appropriate one-pot
synthesis has been selected to study MOFs with simultaneous introduction of both Pd 2+ -
nodes and Pd 0 NPs in one step and test their catalytic activity.

126 Chapter 5
5.2 Preparation and Structure of the Cu/Pd-BTC_1-3
Pd@[Cu3-xPdx(BTC)2]n (Cu/Pd-BTC_1-3) materials have been synthesized under
solvothermal conditions by mixing corresponding metal salts (Pd(OOCCH3)2 and
Cu(NO3)2·3H2O) with H3BTC directly in the starting reactions (see Chapter 7 on
experimental details). All Cu/Pd-BTC_1-3 samples (both as-synthesized and dried
phases) are crystalline solids and isostructural with the parent Cu-BTC (Figures 5.3 and
5.4), indicating the preserved structure integrity after the Pd-sites introduction. Recorded
Figure 5.3. PXRD patterns of the activated Pd@[Cu 3-X Pd x (BTC) 2 ] n (Cu/Pd-BTC_1-3) in
comparison with the activated non-doped Cu-BTC. The vertical dash lines correspond to the peak
position of the (111) planes of the face-centered cubic (fcc) Pd-structure.
PXRD patterns and accordingly calculated cell parameters of Cu/Pd-BTC_1-3 match very
well with the respective simulated data of the reported [Cu3(BTC)2]n single-crystal
structure [35] (Figure 5.5, Table 5.1). Remarkably, intensity of the reflections at ca. 6.67,
9.40 and 13.34° (2θ) assigned to the (200), (220) and (400) planes, respectively, varies
(Figure 5.3). This indicates certain changes of electronic density compared to the nondoped
Cu-analogue (Cu-BTC). The main contribution to the reflection of the (200) and
(220) planes is due to the metal-nodes (Figure 5.6). Hence, such difference in intensities
should primary stem from the partial substitution of Cu 2+ by Pd 2+ within the M2-
paddlewheel units of MOFs. Thus, it indicates Pd 2+ framework incorporation. Considering
the presence of Pd NPs in the discussed Cu/Pd-BTC_1-3, small reflections at 40.02°
resulting from (111) planes of the face-centered cubic structure of Pd [286] are observed

Chapter 5 127
(Figure 5.3). This is probably due to the rather small particle size of these Pd NPs and,
therefore, hard to be detected by PXRD technique. Finally, it should be pointed out, that
employing equal molar amounts of Cu- and Pd-salts or only Pd-precursor in the starting
reaction mixtures, formation of only metal/metal-oxide products has been observed
(Figures 7.25 and 7.26).
Figure 5.4. PXRD patterns of the as-synthesized Pd@[Cu 3-X Pd x (BTC) 2 ] n in comparison with
simulated patterns of the non-doped Cu-BTC.
Table 5.1. Calculated cell parameters of the Cu/Pd-BTC_1-3 (TOPAS academic software and
Pawley method [287] have been employed) in comparison with that obtained from the single crystal
data of the reported [Cu 3 (BTC) 2 ] n . [35]
Sample a (Å) V (Å 3 ) Space group R wp R exp
[Cu 3 (BTC) 2 ] [35] n 26.343 18280 Fm-3m - -
Cu/Pd-BTC_1 26.308 18208 Fm-3m 6.018 4.79
Cu/Pd-BTC_2 26.305 18203 Fm-3m 6.618 5.17
Cu/Pd-BTC_3 26.293 18178 Fm-3m 7.201 6.09

128 Chapter 5
Figure 5.5. Pawley Fits of the samples Cu/Pd-BTC_1-3. Blue, olive and magenta lines represent
the fitted patterns of Cu/Pd-BTC_1, 2 and 3, respectively. Black ticks - theoretical positions of the
Bragg reflections; black crosses - the experimental data; violet lines - the difference between fitted
and measured patterns.

Chapter 5 129
Figure 5.6. Crystal structure of the Cu-HKSUT-1 ([Cu 3 (BTC) 2 ] n ) viewed along the plane (200) (a),
plane (220) (b )and plane (222) (c).

130 Chapter 5
5.3 Compositional characterization and sorption properties of the prepared
Cu/Pd-BTC_1-3
AAS analysis of the activated Cu/Pd-BTC_1-3 solids confirms quantitative incorporation
of palladium. Thus, the Pd-contents and Pd : Cu ratios in the final Cu/Pd-BTC_1-3 samples
remain almost unchanged with respect to the taken feeding ratios of the metal-precursors
(Table 5.2). Further, SEM-EDX elemental mapping demonstrates quite homogeneous
Cu/Pd distribution within obtained Cu/Pd-BTC solids (Figure 5.7).
Table 5.2. Feeding and observed contents of Pd in respect to the total metal amount in Pd@[Cu 3-
xPd x (BTC) 2 ] n (Cu/Pd-BTC_1-3). The incorporation Pd-percentages were calculated based on the
AAS results.
Sample feeding (molar%) obtained (molar%) obtained wt%
Cu/Pd-BTC_1 10 9 3.9
Cu/Pd-BTC_2 15 14 6.2
Cu/Pd-BTC_3 20 20 9.2
Figure 5.7. EDX elemental mapping of the Cu/Pd-BTC_3 solid (red – Cu; green – Pd).
Incorporation of Pd 2+ into the framework as well as the Pd 0 NPs loading has been
subsequently corroborated by high-resolution XPS. Figure 5.8 shows the Pd 3d core-level
spectra of the Cu/Pd-BTC_1 and Cu/Pd-BTC_3 (representative samples with relatively
low and high Pd-contents). Three Pd 3d doublets (3d5/2 and 3d3/2) are resolved in the
deconvoluted spectra. The doublet located at 337.9 and 343.2 eV (Pd2) is characteristic
for Pd 2+ species (Table 5.3). [288-289] In addition, the higher binding energies observed at
338.9 and 344.2 eV for Pd1 reveal the presence of an electronically modified Pd 2+ species.
Moreover, we could unambiguously rule out an assignment of both Pd 2+ species to PdO

Chapter 5 131
NPs, as no typical O 1s peak at about 530 eV has been detected in the corresponding
spectra, which showed only one O 1s peak at 531.8 eV originating from the carboxylate (-
COO) groups in the frameworks. Therefore, both found Pd 2+ species (Pd1 and Pd2) very
likely are associated with the formation of Pd-Pd and Cu-Pd framework-nodes. The
doublet at ca. 335.8 and 341.0 eV is attributed to metallic Pd 0 species (Pd3), indicating the
existence of Pd metallic NPs in these samples. Besides, the amount of Pd 0 NPs in the total
Pd species (Pd 2+ and Pd 0 ) increases (from 33 % for Cu/Pd-BTC_1 to 44 % for Cu/Pd-
BTC_3) along with the doping increase of Pd(II) acetate. TEM characterization has not
been performed because of the beam sensitivity of HKUST-1, which does not allow
characterization of the "pristine" Pd@[Cu3-xPdx(BTC)2]n sample as well.
Figure 5.8. Pd 3d region of the deconvoluted XP spectra of the activated solids Cu/Pd-BTC_1 and
3. Figure is provided by Dr. Y. Wang.

132 Chapter 5
Table 5.3. The assignment of binding energies as well as the determined molar fraction of Pd 2+
and Pd 0 in Cu/Pd-BTC_1 and _3.
Sample
Binding energy, eV
Molar fraction (%)
Assignment
Pd 3d 3/2 Pd 3d 5/2 Pd 2+ : (Pd 2+ +Pd 0 ) Pd 0 : (Pd 2+ +Pd 0 )
Cu/Pd-BTC_1
Cu/Pd-BTC_3
344.2 338.9 Pd 2+ (Pd1)
343.2 337.9 Pd 2+ (Pd2)
340.9 335.6 Pd (Pd3)
344.2 338.9 Pd 2+ (Pd1)
343.2 337.9 Pd 2+ (Pd2)
341.2 335.9 Pd (Pd3)
67 33
56 44
Figure 5.9. IR spectra of the activated samples Cu/Pd-BTC_1-3 in comparison with the parent
Cu-BTC as well as H 3 BTC and Pd-acetate.
Furthermore, any vibrations stemming neither from the non-reacted H3BTC linker nor
used metal-precursors (i.e., acetate-, nitrate-groups) could be revealed in the FT-IR

Chapter 5 133
spectra of all prepared Cu/Pd-BTC solids (Figure 5.9). Moreover, 1 H-NMR spectra of the
digested Cu/Pd-BTC_1-3 samples show presence of only BTC-linker (Figure 5.10). Thus,
absence of the resonances at about 1.9 ppm stemming from the acetate protons fully
supports IR results ruling out any residuals of the employed starting Pd-reactant. Hence,
the presence of Pd 2+ -sites should originate from the in-framework nodes rather than Pd 2+ -
precursor loading.
Figure 5.10. 1 H-NMR spectra of the digested activated Cu/Pd-BTC_1-3 samples. The vertical dash
line stands for the position where the peak of CH 3 -protons from the acetic acid commonly appears.
TGA suggests that thermal stability of the obtained Cu/Pd-BTC_1-3 solids is fully
preserved (in comparison with the parent Cu-BTC) [35] with the decomposition
temperatures close to 300 °C (Figure 5.11). The N2 (77 K) sorption isotherms recorded
for obtained samples reveal type I isotherm (Figure 5.12), confirming their permanent
microporosity. Brunauer-Emmett-Teller (BET) surface area of Cu/Pd-BTC_1 and _2
increase a little in comparison with parent Cu-BTC (prepared under similar conditions)
(Table 5.4), indicating that the presence of Pd 2+ incorporation as metal nodes in the

134 Chapter 5
framework are dominant. When it turns to Cu/Pd-BTC_3, the increasing of Pd 0 NPs
species results in a slight lower BET surface area in comparison with the others samples.
Figure 5.11. TG curves of the prepared Pd-doped solids Cu/Pd-BTC_1-3 in comparison with the
“non-doped” material Cu-BTC.
Table 5.4. BET surface area (S BET ) of Cu/Pd-BTC_1-3 in comparison with the “non-doped” Cu-
BTC.
Sample S BET (m 2 /g) S BET (m 2 /mmol)
Cu-BTC 1561 944
Cu/Pd-BTC_1 (9 mol% of Pd) 1594 982
Cu/Pd-BTC_2 (14 mol% of Pd) 1750 1090
Cu/Pd-BTC_3 (20 mol% of Pd) 1112 700

Chapter 5 135
Figure 5.12. N 2 sorption isotherms collected at 77 K for the non-doped [Cu 3 (BTC) 2 ] n (Cu-BTC) and
Pd-doped solids Pd@[Cu 3-x Pd x (BTC) 2 ] n (Cu/Pd-BTC_1-3).

136 Chapter 5
5.4 Synthesis, compositional characterization and sorption properties of Cu/Pd-
BTC_4
Before the further investigation on catalytic reaction, it is important to prepare analogous
samples featuring dominant extra-framework Pd 0 NPs loading as well. As known from the
earlier experiments, employing higher Pd(II) acetate (more than 20%) in the starting
reaction mixture, will only lead to the formation of metal/metal-oxide products.
Interestingly, PdCl2 exhibits a rather distinct coordination mode with Pd(II) acetate. [290-
292] Besides, longer reaction time in solvothermal conditions could facilitate the creation
of Pd NPs to some extent. Thus, it is expected that higher Pd 0 NPs dispersion can be
reached in Cu/Pd-BTC_4 by altering the Pd-precursor to PdCl2 and extending the reaction
time.
Figure 5.13. PXRD patterns of the as-synthesized (_as) and activated (_ht) Cu/Pd-BTC_4 in
comparison with the patterns simulated from the single crystal XRD data of the reported
[Cu 3 (BTC) 2 ] n (Cu-BTC_sim). [35]

Chapter 5 137
The phase purity and good crystallinity of Cu/Pd-BTC_4 have been proved by the
comparison of the PXRD patterns (Figures 5.13) before and after activation with those
simulated from the single crystal XRD data of the reported [Cu3(BTC)2]n (Cu-BTC_sim). [35]
Notably, the PXRD patterns of the Cu/Pd-BTC_4 sample display higher relative intensity
of the (222) reflection, which is different with the intensity of that in the parent Cu-BTC.
This suggests certain electronic modification on the metal nodes in the framework (e.g.
Pd 2+ substitution of Cu 2+ -sites). However, the presence of Pd NPs could not be precisely
determined by PXRD. No apparent reflections at 40.02 and 46.59 °originating from (111)
and (200) planes of the face-centered cubic structure of Pd are found in the PXRD patterns
of the Cu/Pd-BTC_4. [286] This can be due to the rather small particle size of NPs.
Cu/Pd-BTC_4
Cu-BTC
H 3
BTC
4000 3500 3000 2500 2000 1500 1000 500
wavenumber, cm -1
Figure 5.14. IR spectra of the Cu/Pd-BTC_4 solid in comparison with the parent Cu-BTC and the
starting linker H 3 BTC.
In addition, no vibrations stemming from the non-reacted H3BTC linker or employed
metal-precursors (i.e. nitrate groups) could be observed in the FT-IR spectra of the

138 Chapter 5
obtained Pd-doped solid (Figure 5.14), indicating the absence of nitrate from the
employed for the synthesis of Cu/Pd-BTC_4 Cu-salt. The absence of Cl - in the Cu/Pd-
BTC_4 sample is hard to rule out based only on the IR and 1 H-NMR data. Further
characterizations, namely SEM-EDX and XPS, will addresses this issue.
Figure 5.15. SEM images of the Cu/Pd-BTC samples.
Figure 5.16. EDX elemental mapping of the Cu/Pd-btc_4. Red: Cu-mapping; green: Pd-mapping.
Curiously, SEM image of the sample Cu/Pd-BTC_4 displays that its particles have welldefined
octahedral shape and are visibly bigger (ca. 20 μm) compared to the other solid
(Cu/Pd-BTC_3) (Figure 5.15). Thus, variation of the Pd-precursor apparently influences
extent of palladium inclusion and morphology of the Cu/Pd-MOF particles (as also
reflected in the PXRD, Figures 5.13): Pd(II) acetate favors quantitative palladium
incorporation (samples Cu/Pd-BTC_1-3), while PdCl2 somehow decelerates MOF growth,
leading therefore to larger crystals (sample Cu/Pd-BTC_4). SEM-EDX mapping of the
Cu/Pd-BTC_4 solid shows the homogeneous distribution of Pd and Cu in the particles of
framework (Figure 5.16). In addition, the formation of some Pd species where there is no
contribution of Cu has also been observed. These Pd species could be assigned to Pd-Pd
PWs or just Pd NPs. Due to the beam stability of Cu/Pd-BTC under high electron voltage,

Chapter 5 139
it is hard to distinguish these two possibility. To note, no Cl Kα peak could be observed in
the EDX spectrum of the Cu/Pd-BTC_4 (Figures 5.17), suggesting absence (at least in high
concentration) of Cl - or PdCl2.
Figure 5.17. EDX spectrum of the sample Cu/Pd-btc_4 with the assignments of Cl Kα and Cl Kβ
(green lines).
Deconvoluted XP spectra from the Pd 3d region scan has been gathered for the sample
Cu/Pd-BTC_4 (Figure 5.18). In addition to the Pd 3d doublet (Pd 3d3/2 and Pd 3d5/2) of
Pd 2+ at 343.6 and 338.4 eV as well as 342.4 and 337.2 eV (Table 5.5), [288-289] another
doublet appears at 340.9 and 335.7 eV, which can be attributed to Pd 0 in metallic
palladium. Compared with Cu/Pd-BTC_1-3, this sample reveals dominant Pd 0 than in
case of Cu/Pd-BTC_1-3. The concentration of Pd 0 is determined to amount to 70 %.
Likewise, in Cu/Pd-BTC_1-3, only the O 1s peak at 531.8 eV stemming from COO- has
been revealed. Hence, the presence of PdO can be ruled out due to the absence of
corresponding O 1s peak at about 530 eV. Moreover, the peak of Cl 2p in the survey scan
of Cu/Pd-BTC_4 cannot be observed (Figure 5.19), which together with SEM result
proves that the Pd 2+ in the solid is attributed from Pd 2+ /M 2+ -node in the framework rather
than Pd 2+ -precursor or PdO loading on the framework.

140 Chapter 5
Figure 5.18. Deconvoluted XP spectra of the Cu/Pd-BTC_ 4 in the Pd 3d region. Figure is provided
by Dr. Y. Wang.
Figure 5.19. XPS survey scan of the activated sample Cu/Pd-BTC_4. Figure is provided by P. Guo.

weight loss, %
Chapter 5 141
Table 5.5. The assignment of binding energies as well as the determined molar fraction of Pd 2+
and Pd 0 in Cu/Pd-BTC_4.
sample
Molar fraction (%)
Binding energy, eV
Assignment
Pd 3d 3/2 Pd 3d 5/2 Pd 2+ : (Pd 2+ +Pd 0 ) Pd 0 : (Pd 2+ +Pd 0 )
Cu/Pd-BTC_4
343.6 338.4 Pd 2+ (Pd1)
342.4 337.2 Pd 2+ (Pd2)
340.9 335.7 Pd 0 (Pd3)
30 70
100
90
80
Cu-BTC
Cu/Pd-BTC_3
Cu/Pd-BTC_4
70
60
50
40
100 200 300 400 500 600
T, C
Figure 5.20. TG curves of the activated Cu/Pd-BTC_4 and _5 solids in comparison with the parent
Cu-BTC and Cu/Pd-BTC_3.
In order to gain information on the quantitative incorporation of palladium, AAS analysis
of the activated Cu/Pd-BTC_4 solids has been performed. Thus, with respect to the taken
feeding ratios of the metal-precursors (20%), amount of the incorporated Pd in Cu/Pd-
BTC_4 sample is 12%, which is a little lower than that in Cu/Pd-BTC_3 (20%). TGA of the
Cu/Pd-BTC_4 (Figure 5.20) demonstrates the preserved thermal stability after palladium
introduction and show the framework decomposition after 300 °C. Interestingly, N2

V, cm 3 /g
142 Chapter 5
sorption isotherms recorded at 77K for Cu/Pd-BTC_4 sample show type I isotherms
(Figure 5.21), suggesting the microporosity. This is in analogy to other Cu/Pd-BTC
samples described above. The higher BET surface area of Cu/Pd-BTC_4 (Table 5.6) than
Cu/Pd-BTC_1-3 points to external Pd-NPs rather than included particles into the volumes
of the framework. Besides, from the above described better crystallinity revealed in PXRD
patterns as well as the well-shaped of the particles in SEM image, it is not surprised that
this sample prepared from PdCl2 exhibit higher SBET.
500
450
400
350
300
250
200
150
100
50
/ Cu-BTC
/ Cu/Pd-BTC_3
/ Cu/Pd-BTC_4
0
0.0 0.2 0.4 0.6 0.8 1.0
relative pressure, p/p 0
Figure 5.21. N 2 sorption isotherms collected at 77 K for the non-doped [Cu 3 (BTC) 2 ] n (Cu-BTC) and
solids [Cu 3-x Pd x (BTC) 2 ] n (Cu/Pd-BTC_3-4).
Table 5.6. BET surface areas calculated from N 2 sorption isotherms (77 K) of Cu/Pd-BTC samples
in comparison with the parent Cu-BTC.
Sample
BET surface area (m 2 /g)
Cu-BTC 1561
Cu/Pd-BTC_3 1112
Cu/Pd-BTC_4 2000

Chapter 5 143
5.5 Catalytic test reaction
Both Pd 2+ -containing MOF ([Pd(2-pymo)2]n, 2-pymo = 2-pyrimidinolate) [276-277, 293] and
Pd 0 @MOF [272-273, 281-282] have been reported as good reusable catalysts in typical
palladium-catalyzed reactions such as Suzuki C–C couplings and hydrogenation. Owing to
both Pd 0 NPs and potential Pd 2+ -CUS (that should be available after thermal treatment
and specifically promote H2 splitting) in obtained Pd-doped Cu/Pd-BTC materials, it was
of interest to test their catalytic activity.
Figure 5.22. Concentration of PNP as a function of time for non-doped Cu-BTC and Pd containing
Cu/Pd-BTC_1-4 as catalysts in the aqueous-phase hydrogenation of PNP with NaBH 4 to PAP. The
insert shows the initial reaction rate for Cu/Pd-BTC_1-4 normalized to the amount of Pd in the
catalyst, respectively. Reaction conditions: c PNP = 0.18 mmol dm −3 , c NaBH4 = 0.60 mmol dm −3 , T =
298 K, stirring speed = 1300 min −1 , m catalyst = 5.0 mg, ambient pressure. Figure is provided by Z.
Chen.
As a test reaction, the aqueous-phase hydrogenation of PNP to PAP using NaBH4 as a
reducing agent has been chosen. It can be conducted at room temperature and ambient
pressure within reaction times < 10 min using a simple on-line UV-Vis spectroscopy to
monitor the progress of the reaction. [281, 294-295] The concentration of PNP as a function of

144 Chapter 5
time as well as the initial reaction rate normalized to the amount of Pd in the catalyst for
Cu/Pd-BTC_1-4 are depicted in Figure 5.22. Before addition of the solid catalyst, i.e.,
within the first 0.5 min of the experiment, no PNP conversion was observed. Complete
conversion of PNP to PAP was reached within 2 min of reaction time using Cu/Pd-BTC_1-
4, whereas the conversion of PNP remained incomplete for the Pd-free Cu-BTC. This
incomplete conversion is known for catalysts with low activity and results from
unproductive NaBH4 decomposition to hydrogen. [294] Evidently, the Pd-containing Cu-
BTC catalysts are significantly more active than the Pd-free Cu-BTC. Interestingly, the
initial reaction rate related to the Pd amount for Cu/Pd-BTC_1 and 2 (i.e., 4.0×10 -3 and
2.0×10 -3 dm -3 min -1 ) is significantly higher than that achieved over a metallic Pd catalyst
supported on an Al-containing mesocellular silica foam (1.0×10 -3 dm -3 min -1 ) under the
same reaction conditions. [296] Note that the activity of Cu/Pd-BTC_1 and 2 is so high that
the difference in their catalytic activity cannot be distinguished under the reaction
conditions used.
Figure 5.23. PXRD patterns of the sample with 14% of Pd-doping after the hydrogenation of PNP
to PAP (Cu/Pd-BTC_2_cat) in comparison with that one before the reaction (Cu/Pd-BTC_2). The
diamond symbol represents the reflection position of Cu 2 O, which could be present due to the
reduction by NaBH 4 .

Chapter 5 145
Surprisingly, the normalized initial reaction rate decreases with increasing overall Pd
content from 4×10 -3 dm -3 min -1 for Cu/Pd-BTC_1 to 1.0×10 -3 dm -3 min -1 for Cu/Pd-BTC_3,
respectively (insert in Figure 5.22). This can be explained by considering the decreasing
concentration of Pd 2+ species with increasing Pd content from Cu/Pd-BTC_1 to Cu/Pd-
BTC_3 as observed by XPS (Table S3). Especially, Cu/Pd-BTC_4 containing the lowest
concentration of Pd 2+ species (70%) display the lowest initial reaction rate in comparison
with the other three Cu/Pd-BTC samples. It may, therefore, be concluded that Pd 2+
species in the catalyst are catalytically active and that they are dominantly responsible for
the observed high catalytic activity. Moreover, it has been reported that Pd 2+ can act as
active metal sites in olefin hydrogenations. [276-277, 293] To note, PXRD patterns of the
Cu/Pd-BTC samples before and after reaction indicate that the structure of the
framework stays unchanged (Figure 5.23). Finally, according to the ICP-OES analysis of
the solution after reaction (Cu/Pd-BTC_2 as selective catalysts), leaching of palladium is
negligible (i.e., 0.01mg/L), indicating the stability of the used MOF catalysts as well as the
heterogeneous nature of the catalytic reaction.

146 Chapter 5
5.6 Conclusions
In summary, via one-pot synthesis crystalline porous Pd@[Cu3-xPdx(BTC)2]n MOFs with
various doping levels of Pd have been successfully obtained. On the basis of entire
experimental data, structural incorporation of Pd 2+ serving as frameworks-nodes (within
Cu-Pd or/and Pd-Pd paddlewheels) as well as Pd 0 NPs dispersion in the framework of
HKUST-1 are concluded. To best of our knowledge, it is the singular case of MOFs bearing
both Pd 2+ -paddlewheels and Pd NPs known so far. Curiously, certain dependency of the
crystals morphology of Cu/Pd-BTC and extent of relative ratio of Pd-NPs and Pd 2+ -nodes
on the employed Pd-precursors could be traced. Moreover, distinct Pd sites, especially
Pd 2+ /M-CUS considerably enhances MOFs performance in the aqueous-phase
hydrogenation of PNP to PAP comparing to the “Pd-free” Cu-BTC catalysts, which affords
a perspective way to tune their catalytic activity. Furthermore, a synthesis of HKUST-1
analogs excluding Pd 0 formation and featuring exclusive Pd 2+ /Cu 2+ mixed-metal PWs
would lead to highly active catalysts.

6 Summary and Outlook
Among all MOF’s features, one of the most important and interesting characteristics is the
presence of coordinatively unsaturated metal sites (CUS). Due to much stronger affinity
of many “bare” metal-ions towards some gases (e.g. H2, CO2, CH4) and organic molecules,
design of CUSs within MOFs has been a key factor in enhancing MOFs performance in a
variety of applications such as gas storage, gas selectivity and catalysis.
HKUST-1 ([Cu3(BTC)2]n, Cu-BTC) represents one of the well-known and investigated
MOFs where removal of the coordinated water molecules and, thus, generation of CUSs
could be easily achieved upon heating under vacuum. Moreover, [Ru3(BTC)2Yy]n (Ru-
BTC), which is mixed-valence ruthenium structural analog of HKUST-1, has been
elaborated. Interestingly, this ruthenium MOF exhibits sufficient chemical as well as
thermal stability, and offers rich photo/redox chemistry. Hence, in this dissertation Cuand
Ru-MOFs of [M3(BTC)2Yy]n family (M = Cu, Ru, Mo, Cr, Ni, Fe; x = 0 or 1.5, respectively)
have been chosen as candidates to study the modification of MOF’s local structures (via
modification of CUSs, defects engineering, for instance) and its impact on their properties.
First of all, controlled secondary building units approach (CSA) has been employed to
study the (optimized) formation of isostructural Ru II,II and Ru II,III analogs of HKUST-1.
Notably, compared to the Cu-BTC, the composition and local structure of the Ru-BTC
([Ru3(BTC)2Yy]n·G g) turn to be more complex due to the mixed-valence oxidation state of
Ru-centers. The last requires presence of additional counter-ions X from the employed
Ru-SBUs to compensate the charge of [Ru2] 5+ PW units. Besides, some crucial synthetic
parameters like solvents mixture (H2O: AcOH = 1:0.05) lead to the presence of residual
acetic acid/acetate (as counter-ions X, guest molecules/species G or both) in the final
frameworks. By utilizing distinct Ru II,III -SBUs (either [Ru2 II,III (OOCR)4X] or
[Ru2 II,III (OOCCH3)4]A) with various nature of counter-ions X and A and alkyl groups -R, the
local environment of the metal sites in the obtained isostructural MOF solids could be
tuned to a certain extent. Thus, employment of the [Ru2 II,III (OOCCH3)4]A (where A is a
weakly coordinating anion) instead of [Ru2 II,III (OOCR)4X] (where X is a strongly

148 Chapter 6
coordinating anion), facilitates to decrease the amount of coordinated counter-ions in the
framework of Ru II,III -BTC. Additionally, solvent exchange procedure is another way to
remove residual AcO(H), which is occluded within the framework’s pores or strongly
coordinated to the Ru-sites. Furthermore, the usage of the mono-valence Ru II,II -SBU
([Ru2 II,II (OOCCH3)4]) without any counter-ions has turned to be an optimized way to
prepare highly porous Ru II,II -BTC MOF featuring more accessible Ru-CUSs in comparison
with its mixed-valence Ru II,III -BTC variant.
Secondly, modification of the metal PWs in [M3(BTC)2Yy]n has been accomplished by inframework
incorporation of a scope of di-topic isophthalate (ip) defect generating linkers
DLs (5-X-ip, X = OH, H, NH2 or Br). Remarkably, two kinds of structural defects have been
found in the obtained crystalline and isostructural DEMOFs. One type (A) represents
modified PW nodes featuring reduced metal sites, while the other one (type B) is
associated with the missing PW nodes. In fact, the abundances of these two defect types
depend on the choice of the functional group X in the DLs, doping level of DL as well as the
chosen MOF matrix (i.e., Cu-BTC or Ru-BTC). Moreover, the defects of type A and B in Ru-
DEMOFs seem to play a key role in sorption of small molecules (i.e., CO2, CO, H2) and
catalytic activity (i.e., in ethylene dimerization and Paal-Knorr reaction). Thus,
investigations performed on the Ru-DEMOF and Cu-DEMOF solid solutions have shown
rather a complex picture. Still, the studies on the defects characterization have pave up
the way to more deep understanding of the nature of created defects and defects
engineering in MOFs in general.
Apart from the mixed-linker solid solution approach, mixing of distinct metal-ions via onepot
synthesis has also been utilized to successfully obtain Pd-doped solids Pd@[Cu3-
xPdx(BTC)2]n. To note, simultaneously structural incorporation of palladium within Pd-Pd
and/or Pd-Cu PWs as framework-nodes and Pd nanoparticles (NPs) dispersion has been
achieved for the first time. Interestingly, employing prepared Pd-doped Cu/Pd-BTC as
catalysts revealed their enhanced activity (in comparison with the intact Cu-BTC), namely
in aqueous-phase hydrogenation of p-nitrophenol (PNP) to p-aminophenol (PAP) using
NaBH4 as a hydrogen source. Furthermore, the stability and heterogeneous nature of the
catalysts have been confirmed.
All in all, the studies presented in this dissertation provide a deep insight into the
formation and structure of the complex Ru-BTC. Moreover, creation of various types of
structural defects has been gained and analyzed in its defects-engineered variants (Ru-

Chapter 6 149
DEMOFs). These results are essential for further studies on elaboration of the related
DEMOFs. For example, one may avoid many complications by means of employing Ru II,II
SBUs (instead of mixed-valence Ru II,III -SBUs) to form respectively Ru II,II -MOF, which could
by subsequently used as a matrix for defects engineering. From the other side, the doping
of Pd 2+ into less “complicated” Cu-BTC (because of more substitution labile Cu 2+
precursors) has open a way to exploit more functionality of the resulting MOFs. What
more challenging is, to strictly exclude any reducing parameters during synthesis and
prepare a Pd 0 free Pd 2+ /Cu 2+ mixed-metal analog of HKUST-1. Due to the specific
palladium features (like ability to split H2, etc.), this mixed-metal Cu/Pd-BTC materials
including the defect engineering should hold huge promises for many applications. For
instance, gas sorption (e.g. hydrogen uptake), conductivity (TCNQ loading on Cu/Pd-BTC
to modify the electron density at the metal sites, TCNQ = tetracyanoquinodimethane),
catalysis (e.g. using Cu/Pd-BTC as catalysts in alcohol oxidation, cross coupling reaction,
etc.) are topics worth being studied. Last but not the least, phase pure mixed-component
MOFs, structural analogs of HKUST-1, incorporating both Zn 2+ and Cu 2+ ions, H3BTC and
5-nitroisophthalic acid defect linker have been obtained as well (See chapter 7.5).
However, MOFs with only quite low concentration of the incorporated Zn 2+ (about 3%)
have been obtained during this initial study. In a long run, such combination of mixedmetal
and defect linker within single-phased framework could also be very attractive for
advanced properties owing to the more factors (“tuning keys”) influencing modification
on the metal sites.

7 Experimental Section
In this Chapter various experimental and analytical procedures are given. In the first part,
general analytical procedures and methods broadly used for characterization of the
prepared MOF materials in this work are provided. In the second part, synthetic
procedures as well as supplementary analytical details are described for each Chapter.
7.1 General methods
7.1.1 X-ray Diffraction (XRD)
Powder XRD (PXRD) for all the bulk as-synthesized samples and most of the activated
samples were performed by Dr. M. Tu, S. Wannapaiboon, and W. Zhang on an X’ Pert PRO
PANalytical equipment (Bragg–Brentano geometry with automatic divergence slits,
position sensitive detector, continuous mode, room temperature, Cu-Kα radiation(λ =
1.54178 Å), Ni-filter, in the range of 2θ = 5–50, step size 0.01). Activated sample were
prepared on a silicon wafer in an Ar-filled glovebox right before the measurement starts.
For the measurement of activated samples (Ru-DEMOFs series 1 and 3), the data were
collected by W. Zhang with the assistance of Dr. C. Sternemann, A. Schneemann, and S.
Wannapaiboon at beam line BL9 of the synchrotron radiation facility DELTA at a
wavelength of 0.4592 Å using a two-dimensional MAR345 image plate detector. The
sample was filled into standard capillaries (0.5-mm diameter) in an Ar-filled glovebox and
measured. The data were integrated using the program package Fit2D [297] and
transformed to the CuKα radiation used for all other PXRD measurements on reported
materials for the convenient comparison. PXRD of some other activated samples were
collected by Dr. K. Khaletskaya, C. Rösler, and I. Schwedler in a D8-Advance Bruker AXS
diffractometer with CuKα radiation at 25 °C (Göbel mirror; θ–2θscan; 2θ= 5–50°; step size
= 0.0142 (2θ); position sensitive detector; α-Al2O3 as external standard. The sample was
filled into 0.7 mm diameter standard capillaries in an Ar-filled glovebox and measured in
Debye-Scherrer geometry. All the data were interpreted/analyzed by W. Zhang.

Chapter 7 151
Single crystal XRD data for Ru-SBU were collected on an Oxford Supernova with Atlas
detector (Cu-Kα 1.54184 Å) by Dr. K. Freitag and M. Winter. The crystals were coated with
a perfluoropolyether, collected with a glass fiber loop under a microscope and mounted
in the nitrogen cold gas stream of the diffractometer. For the air-sensitive crystals, they
were transferred from a Schlenk tube in an argon stream onto a specimen holder with
perfluoro-polyalkylether before being picked up with the glass fiber loop. The structural
solution and refinement were done M. Winter and W. Zhang (with the assistance of, Dr. A.
Puls, and Dr. S. Henke) using the program suite Olex2 [298] with the executables SHELXS97
and SHELXL97. [299] For refinement the full-matrix least squares on F2 method was
employed. All non-hydrogen atoms were refined anisotropically while the hydrogen
atoms were calculated and refined with isotropic character.
7.1.2 FT-IR spectroscopy
Conventional FTIR spectra were collected by W. Zhang on a Bruker Alpha FTIR instrument
in the ATR geometry with a diamond ATR unit in the range 400–4000 cm -1 inside a
LABStar MB 10 compact MBraun glove-box (argon atmosphere).
Ultra High Vacuum (UHV) FT-IR measurements were performed using a novel UHV-FTIRS
apparatus (state‐of‐the‐art vacuum IR spectrometer (Bruker, VERTEX 80v) coupled to a
novel UHV system (Prevac)) [300] by our collaboration partners, M. Kauer and P. Guo (the
group of Dr. Y. Wang,) in the Laboratory of Industrial Chemistry (Prof. Dr. M. Muhler),
Ruhr‐University Bochum. The sample transfer to the instrument, data acquisition and
interpretation were carried out by M. Kauer and P. Guo. The discussion of the selected
data and the experimental/synthetic work documented in the thesis were done by W.
Zhang. The powder samples were first pressed into a stainless steel grid (0.5 x 0.5 cm)
covered by gold and then mounted on a sample holder, which was specially designed for
the FTIR transmission measurements under UHV conditions. The grid was cleaned by
heating up to 850 K to remove all contaminants formed on it during preparation. The base
pressure in the measurement chamber was 5 x 10 -11 mbar. The optical path inside the IR
spectrometer and the space between the spectrometer and UHV chamber were also
evacuated to avoid atmospheric moisture adsorption resulting in a high sensitivity and
stability. The MOF samples were cleaned in the UHV chamber by heating to 500 K in order
to remove the contaminants involved during synthesis and all the adsorbed species such

152 Chapter 7
as water and hydroxyl groups. Prior to each exposure, a spectrum of the clean sample was
recorded to be as a background reference. The exposure of the sample to CO and CO2 was
carried out by backfilling the measurement chamber through a leak valve. All UHV-FTIR
spectra were collected with 512 scans at a resolution of 4 cm -1 in transmission mode. The
figures below show the UHV-FTIR apparatus (Figure 7.1) and the schematic
representation of the whole optical path of the IR beam in both reflection and
transmission geometries (Figure 7.2).
Figure 7.1. The UHV‐FTIRS apparatus in (a) perspective view and (b) top view. The labeled
components are: (1) load‐lock, (2) distribution, (3) magazine, (4) measurement (FTIR) chambers,
(5) sample manipulator, (6) vacuum FTIR spectrometer, (7) preparation chamber (planned).
Reprinted with permission from Y. Wang, A. Glenz, M. Muhler, C. Wöll, Rev. Sci. Instrum. 2009, 80,
113108‐6, with the permission of AIP Publishing. [300]

Chapter 7 153
Figure 7.2. Schematic representation of different types of IR measurements: (a) reflectionabsorption
at grazing incidence, (b) transmission. Reprinted with permission from Y. Wang, A.
Glenz, M. Muhler, C. Wöll, Rev. Sci. Instrum. 2009, 80, 113108‐6, with the permission of AIP
Publishing. [300]
7.1.3 Nuclear Magnetic Resonance (NMR) Spectroscopy
Liquid phase 1 H-NMR spectra for the digested activated MOFs were measured and
analyzed by W. Zhang on a Bruker Avance DPX-200 spectrometer at 293 K using TMS as

154 Chapter 7
internal standards and normalizing the signals to the DMSO-d6 signal. The samples were
digested in 0.5 ml DMSO-d6 and 0.1 ml DCl (38 wt %)/D2O(99 %) in a NMR tube. Spectra
for Ru-(DE)MOFs were collected with 512 scans and for the other samples with 128 scans.
7.1.4 Thermogravimetric analyses (TGA)
The thermogravimetric analyses (TGA) data were collected and analyzed by W. Zhang
using a TG/DSC NETZSCH STA 409 PC instrument at a heating rate of 5 K min -1 in a
temperature range from 30–600 °C at atmospheric pressure under flowing N2 (N2
,99.999%; gas flow, 20 ml min -1 ). The sample weight is in a range of 7-12 mg. Activated
sample was filled in a crucible with a vial in an Ar-filled glove-box and immediately used
for the measurement.
7.1.5 Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray
spectroscopy (EDX)
SEM images and EDX mapping were recorded from an FEI ESEM Dual Beam TM Quanta 3D
FEG microscope by Dr. K. Khaletskaya and S. Cwik. In order to increase the conductivity
of MOF samples, they were coated with gold by Dr. R. Neuser prior to being loaded in the
instrument. Sample preparation for the SEM measurement and analysis were done by W.
Zhang.
7.1.6 Transmission electron microscope (TEM) and EDX
Bright filed transmission electron microscope (BFTEM) images and EDX spectra for the
composition determination of Ru-DEMOFs were recorded on a Tecnai G 2 F20 equipped
with a Schottky field emission gun operated at an acceleration voltage of 200 kV by Dr. C.
Wiktor at the department of Mechanical Engineering, Ruhr-University Bochum. Data
analysis was done by W. Zhang.
7.1.7 Elemental Analysis / Atomic absorption spectroscopic (AAS)
EA / AAS analysis data for Ru-(DE)MOFs were obtained from the Mikroanalytisches
Laboratorium Kolbe in Mülheim an der Ruhr (http://www.mikro-lab.de/index.html).
Samples were filled into finger schlenks in an Ar-filled glove-box by W. Zhang and

Chapter 7 155
measured under Ar. Atomic absorption spectroscopic (AAS) analysis for mixed-metal
materials to determine Cu, and Pd contents were performed in the Microanalytical
Laboratory of the Department of Analytical Chemistry at the Ruhr‐University Bochum by
K. Bartholomäus. An AAS apparatus by Vario of type 6 (1998) was employed. Data
interpretation was done by W. Zhang.
7.1.8 Gas Sorption
Experiments on sorption of CO2 (298 K) and H2 (77 K) as well as CO (298K) was performed
with assistance of D. J. Xiao and D. Reed (the group of Prof. J. R. Long) at the Department
of Chemistry in the University of California, Berkeley (USA). Part of the N2 sorption data
were collected and interpreted by N. Arshadi at the laboratory of Industrial Chemistry
department (Prof. Dr. M. Muhler) using a Quantachrome Autosorp-1 MP instrument. Most
of N2 sorption data were collected and analyzed by W. Zhang.
CO adsorption (298 K) and the majority of N2 (99.999%) sorption (77 K) measurements
were performed using a Micromeritics 3Flex instrument. The N2 sorption isotherms of Ru-
DEMOFs with defect 5-NH2-ip linker (3a-3d) samples were collected using a
Quantachrome Autosorp-1 MP instrument, optimized protocols and N2 of 99.9995 %
purity. Sorption isotherms of CO2 (298 K) and H2 (77 K) were conducted on a
Micromeritics ASAP 2020 gas adsorption analyzer. The sample cells were cooled with a
liquid nitrogen bath (77 K) or a liquid argon bath (87 K). For room temperature
measurements (298 K) the sample cells were tempered in a water bath.
Calculation of specific surface area and the isosteric heat of adsorption
A method generated from BET theory, which was developed by Brunauer, Emmett, and
Teller in 1938 as an extension of Langmuirs monolayer adsorption to a very simple model
of multilayer physisorption, is commonly employed to calculate the specific surface area
of a porous solid. This area value is usually determined from the data of physisorption
nitrogen isotherms recorded at 77 K.
The BET theory can be derived similarly to the Langmuir theory, but with the
consideration of multilayered gas molecule adsorption, where it is not required for a layer
to be completed before an upper layer formation starts. For the development of the BET
method five assumptions have been made: i) The sample surface is homogeneous; ii)

156 Chapter 7
Uppermost layer is in equilibrium with vapor phase. iii) The heat of adsorption at all sites
is constant and equal to the heat of condensation from the second layer on; iv) There is no
lateral interactions between molecules. v) At saturation pressure, the number of layers
has infinite thickness. Hence, the BET equation could be derived:
p
n a (p 0 − p) = 1
n a m C
+
(C − 1)
n m a C
Here n a is the amount adsorbed, p is the pressure, p0 is the saturation pressure of the
adsorbed gas at a given temperature, n m
a
is the monolayer capacity and C an empirical
constant. The value of C can be associated to the magnitude of adsorbent-adsorbate
interactions. This equation is an adsorption isotherm and can be plotted as a BET plot
where 1/[n a (p0/p-1)] is the y-axis and p/p0 on the x-axis. The linear relationship of the
BET plot is kept only in a pressure region of p/p0= 0.05 - 0.30. For microporous materials
such as MOFs, a even smaller pressure range (p/p0 = 0.02 - 0.10) is usually applied.
Subsequently, the monolayer capacity n m
a
can be derived from the slope of the BET plot.
Consequently, the specific surface area SBET can be calculated from the following equation:
SBET = n m a N A a m /m
p
p 0
where NA is the Avogadro constant and am is molecular cross-section area occupied by a
single adsorbate molecule in the complete monolayer and m the mass of adsorbent. Still,
we should note that the BET theory is developed on basis of the oversimplified model. In
fact, SBET is greatly affected by the nature of the adsorbent as well as the strength of
adsorbate-adsorbent interactions. Microporous solids including MOFs, the pore surface of
which are rather heterogeneous, the above mentioned assumptions are not valid. The
obtained value of the BET surface area (SBET) can be widely used to compare the porosity
of different porous materials and should not be considered as a precise absolute value.
The adsorption isotherms of H2 adsorption at 77 K and 87 K were independently fit with
triple site Langmuir model
n = q sat,Ab A p
1 + b A p + q sat,Bb B p
1 + b B p + q sat,Cb C p
1 + b C p
where n is the molar loading of adsorbate (mmol/g), qsat is the saturation loading of site
A/B/C (mmol/g), b is the Langmuir parameter for A/B/C (bar -1 ), and p the pressure(bar).
After the triple-site Langmuir fits, the exact pressures correspond to the same amount

Chapter 7 157
adsorbed at different temperatures can be plotted. Subsequently, the Clausius−Clapeyron
equation,
−Q st = RT 2 ( ∂lnp
∂T ) n
was used to calculated the isosteric heats of adsorption(-Qst) as a function of the amount
of H2 adsorbed (n). -Qst is a value represent for the average binding energy of an adorbate
at specific surface coverage.
7.1.9 X-ray absorption near edge structure (XANES)
Data acquisition and analysis for XANES were done at beam line BL8 of the synchrotron
radiation facility DELTA by W. Zhang with the assistance of R. Wagner (and A.
Schneemann).
Simplified theory behind XANES
XANES, also known as near edge X-ray absorption fine structure (NEXAFS), is a kind of
absorption spectroscopy showing the features in the X-ray absorption spectra (XAS) of
condensed matter because of the photoabsorption cross section for electronic transitions
from an atomic core level to final states in the energy region of 50-100 eV above the
selected atomic core level ionization energy. X-rays are ionizing electromagnetic radiation
which afford sufficient energy to excite a core electron of an atom to an excited state (an
empty below the ionization threshold), or to the continuum which is above the ionization
threshold. A core hole is the space that a core electron occupied before it absorbs an X-ray
photon and ejected from its core shell. Subsequently, another atomic electron drops down
in to fill the core hole and release energies either through Auger electron ejection or X-ray
Fluorescence.
When the energy of X-ray radiation is scanning through the binding energy region of a
core shell, there will be a sudden appearance of absorption increase, corresponding to
absorption of the X-ray photon by a specific type of core electrons (eg. 1s, 2s, 2p electrons,
etc.). This gives rise to a so-called absorption edge (K, L, M edge, etc.) in the XAS spectrum
due to its vertical appearance. The binding energies of different core electrons are distinct.
Atoms with a higher oxidation state need more energetic X-ray to excite its core level due

158 Chapter 7
to the more tightly bound electron states. Consequently, the absorption edge energy
increases along with the increase of oxidation-state of the absorption site.
Sample measurements details
The collection of XANES spectra was performed at the Ru-K edge (22117 eV) using a Si
(311) monochromator at Beamline BL8 of the synchrotron radiation facility DELTA, TU
Dortmund. The samples were filled into 1 mm caplillaries in an inert Ar atmosphere glovebox
before the measurement. The set-up was acquired using 15cm Ionchamber filled with
Ar as I0, a 15 cm Ionchamber filled with Xe as I1 and a 30 cm Ionchamber filled with Xe as
I2. Approx 30 mm above the sample was the PIN-Diode capturing a relatively wide solid
angle of fluorescence radiation. The energy was calibrated by measuring a metallic Ru foil
as reference simultaneously to each sample scan. The data processing and analysis were
done using the program ATHENA. [301]
7.1.10 X-ray photoelectron spectroscopy (XPS)
XPS spectra were recorded and analyzed by our collaboration partners, P. Guo and Dr. Y.
Wang in the Laboratory of Industrial Chemistry (Prof. Dr. M. Muhler), Ruhr‐University
Bochum. The discussion of the selected data was done by W. Zhang.
XPS measurements were performed in a UHV setup equipped with a high-resolution
Gammadata-Scienta SES 2002 analyzer. A monochromatic Al Kα X-ray source (energy
1486.6 eV) was used as incident radiation. The analyzer slit width was set at 0.3 mm and
the pass energy was fixed at 200 eV for all the measurements. The overall energy
resolution was better than 0.5 eV. A flood gun was used to compensate for the charging
effects. All spectra reported here are calibrated to the C 1s corelevel binding energy at 285
eV. The XP spectra were deconvoluted using the CASA XPS program with a mixed Gaussian
−Lorentzian function and Shirley background subtraction.
7.1.11 High Performance Liquid Chromatography (HPLC)
HPLC measurements to determine the ratio of the organic components were conducted
by Dr. H. B. Albada and M. Strack at the Chair of Inorganic Chemistry I-Bioinorganic
Chemistry (Prof. Dr. N. Metzler-Nolte), Ruhr‐University Bochum.
Experimental setup:

Chapter 7 159
Buffers: A: water/MeCN/TFA – 95/5/0.1 (%, v/v/v); B: MeCN/water/TFA – 95/5/0.1 (%,
v/v/v)
Gradient: start with 100 % A for 5 min; then in 15 min to 75 % B (i.e. 5 %/min); steady at
75 % B for 2.5 min; drop to 100 % A in 5 min (i.e. 20 %/min); steady at 100 % A for 2.5
min.
Column: Prontosil, RP C18‐AQ, with pre‐column; dimensions: 250 x 4.6 mm (length x
internal diameter), particle size: 5 μm; pore diameter: 120 Å (Knauer, Batch No. 2362,
Column SN: CG 108, 25VF184PSJ).
Detection: λ = 254 nm.
Equipment: HPLC‐runs were performed on a Knauer HPLC‐machine.
7.1.12 Catalytic studies
Catalytical tests for Paal-Knorr reaction in Chapter 4 were performed in collaboration
with the group of Prof. A. Corma, in particular by K. Epp (TU Munich) and Dr. F. X. Llabrés
i Xamena, in the Institute of Chemical Technologies (Instituto de Tecnología Química, ITQ),
Polytechnical University of Valencia (Spain). Ethylene dimerization in Chapter 4 was
carried out by W. Zhang with the assistance of M. Gonzalez (the group of Prof. J. R. Long)
in the department of Chemistry, University of California, Berkeley (US). Catalytic reaction
for the hydrogenation of PNP to PAP in Chapter 5 was performed by Z. Chen and M. Al-
Naji (Group of Prof. R. Gläser) in the institute of Chemical Technology, University of
Leipzig. Data for the catalysis was analyzed by W. Zhang with the assistance of these
collaborators.
Gas Chromatography measurements for monitoring the product of Paal-Knorr reaction
were performed on an Agilent Technologies 7890A with FID (Flame Ionization Detector)
using a capillary column HP-5 (5% phenylmethylpolysiloxane) of 30 m length and 0.32
mm internal diameter as well as BP20(WAX) of 15 m length and 0.32 mm internal
diameter as another column. Thereby, the products were measured in high dilution using
volatile organic solvents (usually ethanol or acetone).

160 Chapter 7
7.2 Experimental data on chapter 3
All chemicals (RuCl3·xH2O, LiCl, AgSO4, NaBPh4, AgBF4, pivalic acid, benzene-1, 3, 5-
tricarboxylic acid (H3BTC)) and all solvents (CH3COOH, H2O, CH3OH, EtOH, acetic
anhydride, acetone and hexane) were used as commercially received unless otherwise
noted. Tetrahydrofuran (THF) used in the synthesis of SBU-c was catalytically dried,
deoxygenated, and saturated with argon using an automatic solvent purification system
from MBraun.
7.2.1 Synthesis of the ruthenium precursors ([Ru2(OOCR)4X] and
[Ru2(OOCCH3)4]A)
Scheme 7.1. Preparation of the Ru-SBUs (SBU-a to SBU-d) used for MOF syntheses.
[Ru2(OOCCH3)4Cl] (SBU-a)
This compound was prepared using the method reported in the literature with slight
modification. [202] RuCl3·xH2O (0.5 g, 2 mmol) and LiCl (0.5 g, 11.9 mmol) were mixed in
one flask. Then glacial acetic acid (17.5 ml) and acetic anhydride (3.5 ml) were added.
Subsequently, the mixture was refluxed for 24 h. The resulting red-brown precipitate was
collected, washed several times with acetone, and dried under ambient conditions first
and then under dynamic vacuum for at least 4 h (Yield: 0.33 g).

Chapter 7 161
Figure 7.3. PXRD patterns of [Ru 2 (OOCCH 3 ) 4 Cl] SBU-a in comparison with the simulated patterns
reported. [203]
Figure 7.4. Acid-digested (DCl) 1 H-NMR spectrum of [Ru 2 (OOCCH 3 ) 4 Cl] (SBU-a) in the solvent of
DMSO-d 6 .

162 Chapter 7
[Ru2(OOCC(CH3)3)4(H2O)Cl](CH3OH) (SBU-b)
The synthesis was carried out according to the literature. [201] SBU-a (0.3 g, 0.63 mmol)
was dissolved in 60 ml solution of the H2O : CH3OH (1 : 1) mixture. Later, pivalic acid (0.39
g, 3.79 mmol) was added and the resulting mixture was refluxed. The reaction was
finished after 5 hours, when the solution turned to a red-brown color. This solution was
cooled down and left to stay overnight. As a result, red-brown crystals precipitated. The
final product was collected and washed twice with hexane (Yield: 0.37 g).
Figure 7.5. Schematic description of the molecular structure of SBU-b in the solid state obtained
by single crystal structure analysis. Note the half occupied Cl and half occupied O positions at the
apical position of Ru coordination sphere. The oxygen atoms of the methanol molecule in the
asymmetric unit (solvate) were split into two parts due to disorder. Circle with cross: Ru; circle
shaded: Cl; circle shaded bottom right to top left: O; circle with blank: C. Single crystals of SBU-b
were measured at low temperature (101K) while in the literature reference at 295K. The carbon
atoms in CMe 3 were refined isotropically as well as the centrosymmetric structural model with
partial occupation of Cl and O water as in the reference. [201] However, the measurement in the lower
temperature reported here tends to be of better quality.

Chapter 7 163
Table 7.1. Cell parameters of [Ru 2 (OOCC(CH 3 ) 3 ) 4 (H 2 O)Cl](CH 3 OH) (SBU-b) obtained from single
crystal X-ray diffraction and reported in the literature. [201]
Obtained Literature [201]
Cell
parameters
a = 9.256(4)Å,
b = 9.383(4) Å,
c = 9.605(4) Å;
α = 73.712(4)°,
β = 83.681(4)°,
γ = 73.585(4)°;
V = 767.65(6)Å 3
a = 9.353(3)Å,
b = 9.469(6) Å,
c = 9.804(4) Å;
α = 72.57(4)°,
β = 83.21(3)°,
γ = 73.88(4)°;
V = 795.3(7) Å 3
Figure 7.6. Acid-digested (DCl) 1 H-NMR spectrum of [Ru 2 (OOCC(CH 3 ) 3 ) 4 (H 2 O)Cl](CH 3 OH) (SBUb)
in the solvent of DMSO-d 6 .

164 Chapter 7
Figure 7.7. The PXRD patterns of [Ru 2 (OOCC(CH 3 ) 3 ) 4 (H 2 O)Cl](CH 3 OH) (SBU-b) measured at
different states (immediately after synthesis, one day later and two days later). From the PXRD
patterns, we can infer that when the single crystal stays at room temperature for a while, it will
lose the solvents gradually, which leads to the disappearance of certain reflexes.

Chapter 7 165
[Ru2(OOCCH3)4(THF)2]BF4 (SBU-c)
The compound was synthesized under Ar using the method reported in the literature. [200]
SBU-a (100 mg, 0.211 mmol) and AgBF4 (42 mg, 0.211 mmol) were stirred in dry THF (4
ml) with the protection of tin foil at room temperature. A red solution and white
precipitate of AgCl was obtained after 24 h. The solution was filtered and the precipitate
was washed several times with THF until colorless. All the filtrates were collected
together, and the volume was reduced (ca. 4 times) in vacuum and the product was
obtained (Yield: 108 mg).
Figure 7.8. Acid-digested (DCl) liquid 1 H-NMR spectrum of SBU-c (solvent: DMSO-d 6 ).

166 Chapter 7
[Ru2(OOCCH3)4(H2O)2]BPh4 (SBU-d)
This precursor was synthesized in accordance to the literature procedure. [199] SBU-a (0.48
g, 1.0 mmol) and AgSO4 (0.17 g, 0.5 mmol) were stirred in 20 ml of water at 40 °C. A white
powder (AgCl) precipitated after 10 min and was filtered off. The resulting brown solution
was cooled down to 0 °C, and then the aqueous solution of NaBPh4 (0.4 g, 1.2 mmol) was
added drop-wise while stirring. The orange-brown product precipitated immediately.
Subsequently, it was filtered and washed with cold water three times (Yield: 0.64 g). The
final product was dried in vacuum at room temperature and stored in a fridge.
Figure 7.9. 1 H-NMR spectrum of SBU-d (solvent: DMSO-d 6 ).
[Ru2(OOCCH3)4] (SBU-e)
The precursor SBU-e was obtained according to the reported method. [206-207] RuCl3·xH2O
(4 g) together with 20mg PtO2 were put into a Fischer-Porter bottle in an argon-filled
glove-box. Then 50 mg degassed methanol was added. After the whole system was
degassed, the reactor was pressurized with ca. 2 atm hydrogen. The solution was stirred
for 3 hours until it was deep blue. Subsequently, the solution was filtered under argon into
50 ml degassed methanol which contain 4.7 g Li acetate. After heating under reflux for 18

Chapter 7 167
hours, a deep red brown solution and an orange-brown microcrystalline product were
resulted. The hot solution was filtered and the obtained solid was washed with methanol
(3 x 20 ml). The product was then dried at 80°C under vacuum as a brown powder. m.p.
276 °C.
Scheme 7.2. Synthesis procedure of Ru 2 (OOCCH 3 ) 4 (SBU-e).
Figure 7.10. IR spectra of [Ru 2 II,II (OOCCH 3 ) 4 ] (SBU-e) in comparison with [Ru 2 II,III (OOCCH 3 ) 4 Cl]
(SBU-a). The vertical dash line represents the position of vibrations originated from ν as (COO) and
ν s (COO) in [Ru 2 II,II (OOCCH 3 ) 4 ].

168 Chapter 7
[Ru2(OOCCH3)4](THF)2
Single crystal of [Ru2(OOCCH3)4](THF)2 was obtained in accordance to the reported
procedure. [207] In particular, the sample of [Ru2(OOCCH3)4] was dissolved into
tetrahydrofuran (THF) at 74 °C (oil bath) for 10 min with stirring. Subsequently, the stir
was stopped and the solution was slowly cooled down (10 °C/30 min) to room
temperature in a slow stream of Ar. The solution was then stored in a freezer at -20 °C
overnight giving brown crystals.
Table 7.2. Cell parameters of single crystal [Ru II,II 2 (OOCCH 3 ) 4 ](THF) 2 . Single crystal structure was
not given due to the formation of twin crystal.
obtained literature [207]
a = 14.3787 Å, b = 9.6279 Å,
c = 15.4351 Å; α = 90.000°,
β = 90.000°, γ = 90.000°;
V = 2134.5Å 3
c = 14.606(3)Å a = 9.598(2)Å,
b = 15.803(3)Å; α = 90.00°,
β = 90.00°, γ = 90.00°;
V = 2215.4Å 3
7.2.2 Synthesis of Ru-MOFs [Ru3(BTC)2Xx]·Gg
Scheme 7.3. Syntheses scheme of Ru-MOFs (1-4) employing various SBUs. Reaction Conditions
for 1: CH 3 COOH, H 2 O, 160 °C, 72h; 2: CH 3 COOH, H 2 O, 160 °C, 168h; 3: CH 3 COOH, H 2 O, 160 °C, 72h;
4: CH 3 COOH, H 2 O, 120 °C, 72h.

Chapter 7 169
[Ru3(BTC)2Cl(AcO)0.5]n·(AcOH)1.5(H3BTC)0.1(H2O)4 (1_ex)
This sample was obtained according to the method reported by Kozachuk et al. [82] A
sample of SBU-a (170 mg, 0.36 mmol) and H3BTC (101 mg, 0.48 mmol) were placed in a
20 ml Teflon vessel, and 4 ml of H2O and 0.7 ml of CH3COOH were subsequently added.
The vessel was sealed in an autoclave and kept in a preheated oven at 160 °C for 72 h. The
crude product was filtered and washed several times with distilled water and dried under
ambient conditions (Yield: 171 mg). The obtained powder was further activated by
heating at 150 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).
[Ru3(BTC)2Cl1.2(OH)0.3]n·(H3BTC)0.15(AcOH)2.4(PivOH)0.45 (2_ex)
The sample was prepared in accordance to the reported procedure. [83] A sample of SBUb
(270 mg, 0.42 mmol) and H3BTC (120 mg, 0.57 mmol) were placed in a Teflon vessel,
and then 6 ml of H2O and 0.1 ml of CH3COOH were added. The vessel was sealed in an
autoclave and kept in the preheated oven at 160 °C for 120 h. As a result, a powdered
product was obtained. It was filtered, washed several times with ethanol and dried at
ambient temperature first (Yield: 223 mg). The sample was activated by heating under
dynamic vacuum (ca. 10 -3 mbar) at 150 °C for 24 h.
[Ru3(BTC)2F0.7(OH)0.8]n·(AcOH)1.5(H3BTC)0.2 (3_ex)
A sample of SBU-c (241 mg, 0.36 mmol) and H3BTC (101 mg, 0.48 mmol) were mixed in a
20 ml Teflon vessel with 4 ml of H2O and 0.7 ml of CH3COOH. The vessel was subsequently
sealed in an autoclave and placed in the preheated oven at 160 °C for 72 h. The final brown
product was collected, washed several times with distilled water, and dried under
ambient conditions first (Yield: 265 mg). The sample was further activated by heating at
150 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).

170 Chapter 7
[Ru3(BTC)2(OH)1.5]n·(H3BTC)0.8(AcOH)1.4(H2O)3 (4_ex)
A sample of SBU-d (286 mg, 0.36 mmol) and H3BTC (101 mg, 0.48 mmol), 4 ml of H2O and
0.7 ml of CH3COOH were mixed in a Teflon vessel. The vessel was subsequently sealed in
an autoclave and placed in the preheated oven at 120 °C for 72 h. The final product was
filtered, washed several times with distilled water, and dried under ambient conditions
first (Yield: 191 mg). The material was further activated by heating at 150 °C for 24 h
under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.11. 1 H-NMR spectra of 4 (before solvent exchange) and 4-ex (after solvent exchange) in
comparison with NaBPh 4 .

Chapter 7 171
Figure 7.12. PXRD patterns of the materials obtained from different solvents with a small amount
of acetic acid or without acetic acid as component in the solvent mixture at the same conditions
(160 °C, 72h, solvothermal, starting with SBU-a and H 3 BTC) in comparison with SBU-a and Ru-
MOF 1. a) 4 ml diglyme and 4 drops HCl, b) 4 ml H 2 O and 0.7 ml HCOOH, c) 4 ml H 2 O and 0.7 ml
CF 3 COOH, d) 4 ml diglyme, e) 4 ml H 2 O and 4 drops HCl; f) pH = 1.89 solution of H 2 O and CF 3 COOH,
10 ml (note: the same pH value with the literature; [82] formula: 4ml H 2 O and 0.7ml CH 3 COOH); g)
pH = 1.89 solution of H 2 O and CF 3 COOH, 24 ml; h) pH = 1.89 solution of H 2 O and CF 3 COOH, 4.7 ml;
i) pH = 1.89 solution of H 2 O and HCl, 4.7 ml; j). 12 ml H 2 O and 161 μl CH 3 COOH (pH = 2.47; note
the same pH value with the literature [83] formula: 12ml H 2 O and 161 μl CH 3 COOH). Note: CF 3 COOH
was employed to trace the incorporation of the carboxylic acid by the CF 3 -group.

172 Chapter 7
[Ru3(BTC)2]n∙(AcOH)2.3 (5)
The preparation of Ru-MOF 5 was similar with Ru-MOF 1 using SBU-e (158 mg, 0.36
mmol) and H3BTC (101 mg. 0.48 mmol) with degassed water and AcOH. All the degassed
reactant was then mixed in a Teflon vessel sitting in a schlenk flask under Argon
atomosphere. The vessel was subsequently quickly sealed in an autoclave and placed in
the preheated oven at 160 °C for 72 h. The crude product was filtered and washed several
times with degassed distilled water and dried under vacuum. Further activation of the
powder was performed by heating at 150 °C for 24 h under dynamic vacuum (ca. 10 -3
mbar).
Figure 7.13. 1 H-NMR spectra of the sample 5 ([Ru 3 (C 9 H 3 O 6 ) 2 ] n·(CH 3 COOH) 2.3 ) digested in
DCl/DMSO-d 6 mixture.

Chapter 7 173
7.3 Experimental data on chapter 4
Ruthenium SBU precursor [Ru2(OOCCH3)4Cl]n [202] as well as the parent single-linker Ru-
MOF [82, 198] were prepared following procedures previously described in the literature and
in Chapter 7.2. All other reagents were available commercially and used without further
purification. Before further manipulations, all activated samples were stored in a glovebox
under inert Ar atmosphere.
7.3.1 Synthesis of Ru-DEMOF samples (1a-1d, 2a-2d, 3a-3d, 4a-4c)
[Ru3(BTC)2-x(5-X-ip)xXy]n (X = counter ion; 0.1 ≤ x ≤ 1; 0 ≤ y ≤ 1.5). The samples were
synthesized according to the reported method [138] applying the so-called controlled SBU
approach. The mixtures of parent linker (1,3,5-benzenetricarboxylic acid, i.e. H3BTC) and
defective linker (5-X-isophthalic acid, i.e. 5-X-ip, X = OH (1), H (2), NH2 (3) and Br (4),
respectively) combined with 1.5 molar equivalents of [Ru2(OOCCH3)4Cl]n (0.36 mmol,170
mg) were placed in the 20 ml Teflon vessels. Subsequently, 4 ml of HPLC grade water and
0.7 ml of glacial acetic acid were added. The molar ratios and amounts of the linkers used
in the starting materials are listed in the Table 7.3. The Teflon reaction vessels were then
placed in the Teflon-lined stainless steel autoclaves. The autoclaves were further sealed
and placed into the pre-heated oven at 433 K for 72 h. Afterwards the autoclaves were
taken out and cooled down at room temperature. The resulting powder products were
collected by centrifugation. Afterwards, they were soaked into HPLC grade water (ca. 20
ml) and the solvent was refreshed by the same water amount every 24 hours for 3 times.
Finally, the solvent was removed and collected powders were dried under air at room
temperature. The activation of the solids was performed by heating at 423 K for 24 h
under dynamic vacuum (ca. 10 -3 mbar).

174 Chapter 7
Table 7.3. Feeding molar ratios and amounts of the linkers used in the syntheses of the Ru-
DEMOF samples.
parent linker (H 3 BTC)
defect linker (5-X-ip)
Sample
H 3 BTC : (H 3 BTC + 5-XipH
2 )
mass
(mg)
5-X-ipH 2 : (H 3 BTC + 5-X-ipH 2 )
mass
(mg)
1a 90% 90.8
10% 9
1b 80% 80.7 20% 18
X = OH
1c 70% 71 30% 26
1d 50% 50.5 50% 43.7
2a 90% 90.8
10% 8
2b 80% 80.7 20% 16
X = H
2c 70% 71 30% 24
2d 50% 50.5 50% 40
3a 90% 90.8
10% 8.7
3b 80% 80.7 20% 17.4
X = NH 2
3c 70% 71 30% 26
3d 50% 50.5 50% 43.5
4a 90% 90.8
10% 12
4b 80% 80.7 X = Br
20% 24
4c 70% 71 30% 35.3

Chapter 7 175
Table 7.4. BET surface area (S BET ) values of the Ru-DEMOFs (1a-1d, 2a-2c, 3a-3d, 4a-4c)
compared with the parent Ru-MOF as well as [Cu 3 (BTC) 2 ] n . S BET (m 2 /mmol) of the parent Ru-MOFs
and Ru-DEMOFs 1a, 1c and 1d was converted from the respective measured S BET (m 2 /g) values
according to the proposed composition in Chapter 3 and 4.
Sample S BET , m 2 /g S BET , m 2 /mmol
parent Ru-MOF 1_ex 998 [208] 964
parent Ru-MOF 5 1371 1173
[Cu 3 (BTC) 2 ] n 1734 [83] 1049
1a 1106 1062
1b 1284 -
1c 1302 1232
1d 947 930
2a 1059 -
2b 1023 -
2c 838 -
2d 574 -
3a 1003 -
3b 985 -
3c 975 -
3d 781 -
4a 996 -
4b 847 -
4c 693 -

176 Chapter 7
For comparison of the obtained S BET values for Ru-MOFs with the homologous Cu-MOFs, it might
be more informative using m 2 /mmol units (due to substantial difference in the molecular weight
of Cu and Ru and the presence of guest molecules). Thus, the S BET of the parent Ru-MOF (964
m 2 /mmol) is quite similar to that of a typical reference sample [Cu 3 (BTC) 2 ] n (1049 m 2 /mmol).
More importantly, the S BET of the Ru-DEMOF solids slightly increases in comparison with both
parent analogues. Due to the complexity of the composition (which has been mentioned in the
section 4.2.1.2 of Chapter 4), EA was not performed for the rest Ru-DEMOFs to determine the
unambiguous composition with counter-ions and guest molecules. Hence, S BET values in the unit
of m 2 /mmol were not calculated for them.
Figure 7.14. XPS survey scan of the parent Ru-MOF and Ru-DEMOFs (1a, 1c, 1d, 2a and 2b). 1a,
1c and 1d - 8%, 32% and 37% 5-OH-ip incorporation, respectively; 2a and 2b - 15% and 28% ip
incorporation, respectively. Figure is provided by P. Guo.

Chapter 7 177
7.3.2 Catalytic reactions using Ru-DEMOFs as catalysts
7.3.2.1 Ethylene dimerization
In a typical run (entry 5), 2.1 mg of the activated Ru-MOF 1c was put in a 10 ml steel
reactor followed by adding of 0.81 ml of Et2AlCl (1M in heptane), 2.1 ml of toluene and
0.09 ml of undecane (0.01 M in toluene). After degassing, the reactor was flushed with
C2H4 (800psi) and placed in a pre-heated oil bath at 80 °C with stirring for 2 hours.
Subsequently, the reaction was stopped and the reactor was cooled down at -7 °C in a
mixture of dry ice and ethylene glycol bath. Cold distilled water was added to quench the
reaction. The organic layer kept cold was then quickly analyzed by gas chromatography
(SRI 8610V GC, 60 m x 0.54 mm internal diameter, 5.0 µm MXT-1 capillary columns) using
undecane signal as a reference. In case of no additive, the volume of toluene was changed
to 2.91 ml. Other parameters are the same as entry 5 described above.
7.3.2.2 Paal-Knorr reaction
In a typical run, 5 mg of the activated Ru-MOF/DEMOFs in 0.5 ml of toluene were
introduced into 125 mg (1.1 mmol) of 2,5-hexadione and 95 mg (1 mmol) of aniline and
were stirred at 90 °C for 24h under air. The reaction was followed by taking aliquots every
hour and analyzing the products by GC-MS. The reactions were performed in closed
(pressurize able) reaction vials.
7.3.3 Synthesis of [Cu3(BTC)2]n (Cu-BTC)
[Cu3(BTC)2]n was prepared from a reported method [35] at a litter lower temperature (120
°C). Specifically, Cu(NO3)2∙3H2O (1.8 mmol, 438 mg) and 1, 3, 5-benzentricarboxylic acid
(H3BTC, 1.0 mmol, 210 mg) were put into a Teflon vessel, and a solution of 12 ml H2O:EtOH
(1:1) was added. The vessel was sealed in an autoclave and kept in a preheated oven at
100 °C for 12 h. The crude product was filtered and washed several times with distilled
water and absolute ethanol, respectively. After dried under ambient conditions the
obtained powder (152 mg) was further activated by heating at 120 °C for 24 h under
dynamic vacuum (ca. 10 -3 mbar).

178 Chapter 7
7.3.4 Synthesis of Cu-DEMOF samples (D1-8)
D1
H3BTC (100mg, 0.48 mmol) and ip (80mg, 0.48 mmol) equaling a 1:1 ratio were mixed
with Cu(BF4)2 6H2O (488 mg, 1.4 mmol) and placed into a 20 ml screw jaw. Subsequently
14 ml N,N-Dimethylformamide (DMF) was added. The screw jaw was then sealed and put
into a pre-heated oven at 80 °C for 20 h. The resulting blue powder products were
collected by centrifugation. Afterwards, they were washed by DMF (30 ml x 3), EtOH (30
ml x 3) and acetone (30 ml x 3) subsequently. The final powder was collected and dried
under air at room temperature. The activation of the solids was performed by heating at
170 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.15. 1 H-NMR spectra of the acid-digest D1 sample (solvent: DMSO-d 6 , DCl).

Chapter 7 179
D2
This sample was prepared as D1 using 160mg ip (2 molar equivalent to that of H3BTC)
instead. The resulting blue powder products were separated from the solution by
centrifugation. Afterwards, they were washed by DMF(30 ml x 3), EtOH (30 ml x 3) and
acetone (30 ml x 3) subsequently. Finally, the solvent was removed and the powder was
dried under air at room temperature. The activation of the solids was performed by
heating at 170 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.16. 1 H-NMR spectra of the acid-digest D2 sample (solvent: DMSO-d 6 , DCl).

180 Chapter 7
D3
The mixture of H3BTC (100mg, 0.48 mmol), ip (80 mg, 0.48 mmol) and Cu(BF4)2 6H2O
(488 mg, 1.4 mmol) was placed into a 50 ml Teflon vessel. Subsequently, 24 ml EtOH was
added. The Teflon reaction vessel was then placed in the Teflon-lined stainless steel
autoclaves. The autoclaves were further sealed and placed into the pre-heated oven at 80
°C for 20 h. Afterwards the autoclaves were taken out and cooled down at room
temperature. The resulting blue powder products were separated from the solution by
centrifugation. Afterwards, they were washed by EtOH (30 ml x 3) and acetone (30 ml x
3) subsequently. Finally, the solvent was removed and the powder was dried under
ambient atmosphere at room temperature. The activation of the solids was performed by
heating at 120 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.17. 1 H-NMR spectra of the acid-digest D3 sample (solvent: DMSO-d 6 , DCl).

Chapter 7 181
D4
This sample was prepared as D3 using 160mg ip (2 molar equivalent to that of H3BTC)
instead. The resulting powder products were collected by centrifugation. Afterwards, they
were washed by EtOH (30 ml x 3) and acetone (30 ml x 3) subsequently. Finally, the
solvent was removed and the powder was dried under ambient atmosphere at room
temperature. The activation of the solids was performed by heating at 120 °C for 24 h
under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.18. 1 H-NMR spectra of the acid-digest D4 sample (solvent: DMSO-d 6 , DCl).

182 Chapter 7
D5
This sample was repeated following the reported method. [140] H3BTC (50mg, 0.24 mmol)
and 1 molar equivalent of ip (40mg, 0.24 mmol) combined with Cu(NO3)2·3H2O (171mg,
0.70 mmol) was placed into a 20ml screw jaw. Subsequently, 7 ml DMF and 0.3 ml conc.
HBF4 was added. The screw jaw was then sealed and put into a pre-heated oven at 80 °C
for 20 h. The resulting blue powder products were collected by centrifugation.
Afterwards, they were washed by DMF(30 ml x 3), EtOH (30 ml x 3) and acetone (30 ml x
3) subsequently. The final powder was collected and dried under air at room temperature.
The activation of the solids was performed by heating at 140 °C for 24 h under dynamic
vacuum (ca. 10 -3 mbar).
Figure 7.19. 1 H-NMR spectra of the acid-digest D5 sample (solvent: DMSO-d 6 , DCl).

Chapter 7 183
D6
This sample was obtained as D5 using 80 mg ip instead. [140] The resulting blue powder
products were collected by centrifugation. Afterwards, they were washed by DMF(30 ml
x 3), EtOH (30 ml x 3) and acetone (30 ml x 3) subsequently. The final powder was
collected and dried under ambient atmosphere at room temperature. The activation of the
solids was performed by heating at 140 °C for 24 h under dynamic vacuum (ca. 10 -3 mbar).
Figure 7.20. 1 H-NMR spectra of the acid-digest D6 sample (solvent: DMSO-d 6 , DCl).

184 Chapter 7
The synthesis of D7 and D8 are basically the same as D5 and D6, respectively. The only
difference is that there is no usage of HBF4 during synthesis.
Figure 7.21. 1 H-NMR spectra of the acid-digest D7 sample (solvent: DMSO-d 6 , DCl).
Figure 7.22. 1 H-NMR spectra of the acid-digest D8 sample (solvent: DMSO-d 6 , DCl).

Chapter 7 185
Figure 7.23. PXRD patterns of as-synthesized samples prepared from similar reactant with the
sample D7 and D8 using EtOH instead of DMF (100 °C, 12h) in comparison with patterns
simulated from [Cu 3 (BTC) 2 ] n (Cu-HKUST-1 sim.).

186 Chapter 7
7.4 Experimental data on chapter 5
All chemicals (Cu(NO3)2∙3H2O, Pd(OOCCH3)2, PdCl2, benzene-1,3,5-tricarboxylic acid
(H3BTC), p-nitrophenol (PNP) (99%), Sodium borohydrate (NaBH4) (98%)) and all
solvents (H2O, ethanol, and acetone) were used as commercially received unless
otherwise noted. Before further manipulations, all activated samples were stored in an
Ar-filled glove-box.
7.4.1 Synthesis of [Cu3-XPdx(BTC)2]n
Cu/Pd-BTC_1-3
For Cu/Pd-BTC_1-3, 2.0 mmol of H3BTC (420 mg) was combined with 1.8 molar
equivalents of a mixture of Cu(NO3)2∙3H2O and Pd acetate and then placed into a Teflon
vessel. Subsequently 15ml of H2O/ethanol (1:1) solution was added. The molar
percentage and amount of each metal salts in the total metal source as well as their weight
used in the starting reactant are for Cu/Pd-BTC_1, Cu(NO3)2∙3H2O (90%, 3.24 mmol, 783
mg) / Pd acetate (10%, 0.36 mmol. 80.8 mg); for Cu/Pd-BTC_2, Cu(NO3)2∙3H2O (85%,
3.06 mmol, 739 mg) / Pd acetate (15%, 0.54 mmol. 121.2 mg); for Cu/Pd-BTC_3,
Cu(NO3)2∙3H2O (80%, 2.88 mmol, 696 mg) / Pd acetate (20%, 0.72 mmol. 161.6 mg). The
Teflon vessel was sealed in an autoclave and kept in the oven at 125 °C for 12h. The
resulting power product was collected by filtration and washed several times with
distilled water and acetone, respectively. After dried under ambient conditions the
obtained powder was further activated by heating at 120 °C for 24 h under dynamic
vacuum (ca. 10 -3 mbar).

Chapter 7 187
Figure 7.24. XPS survey scans of the activated samples Cu/Pd-BTC_1 and 3. Figure is provided
by P. Guo.
Figure 7.25. PXRD patterns of the sample obtained using 50% feeding of Pd(II)-acetate under the
same conditions as [Cu 3-X Pd x (BTC) 2 ] n with 10%, 15% and 20% feeding .

188 Chapter 7
Figure 7.26. PXRD patterns of the sample prepared using only Pd(II)-acetate and H 3 btc under the
same conditions as introduced mixed-metal solids with 10%, 15% and 20% feeding of Pd(II)-
acetate. No Cu-salt was employed.

Chapter 7 189
Cu/Pd-BTC_4
For sample Cu/Pd-BTC_4, 0.48 mmol of H3BTC (101 mg) was combined with 1.5 molar
equivalents of mixture of Cu(NO3)2∙3H2O (80%, 0.58 mmol, 139 mg) / PdCl2 (20%, 0.14
mmol. 25.5 mg) and then placed into a Teflon vessel. Subsequently 6ml of H2O/ethanol
(1:1) solution was added. The Teflon vessel was sealed in an autoclave and kept in the
oven at 90 °C for 16h. The resulting power product was collected by filtration and washed
several times with distilled water and acetone, respectively. After dried under ambient
conditions the obtained powder was further activated by heating at 120 °C for 24 h under
dynamic vacuum (ca. 10 -3 mbar).
Figure 7.27. 1 H-NMR spectra of the acid-digest sample of Cu/Pd-BTC_4 (solvent: DMSO-d 6 , DCl).

190 Chapter 7
7.4.2 Hydrogenation of PNP to PAP
The catalytic aqueous-phase in-situ hydrogenation of PNP to PAP using NaBH4 as a
hydrogen source was carried out in a 100 cm 3 batch reactor at room temperature (298K),
ambient pressure and 1300 min -1 stirring speed. Figure 7.28 depicts the catalytic
experimental setup. In the typical catalytic experiment, 5.0 cm 3 of an aqueous solution of
NaBH4 (0.60 mmol dm −3 ) were added to 45.0 cm 3 of an aqueous solution of PNP (0.18
mmol dm −3 ). The reaction was started by introducing 5.0 mg of the catalyst. PNP
concentration changes were monitored via online UV-vis spectroscopy (AvaSpec-3648,
optical path length: 5 mm) at a wavelength of 400 nm (see Figure 7.29). The initial
reaction rate (r0) was calculated by assuming a zero order reaction from the linear
decrease of PNP concentration after the addition of the catalyst.
Figure 7.28. Experimental setup for aqueous-phase in-situ hydrogenation of PNP to PAP with
NaBH 4 as hydrogen source using an online UV-vis spectrometer. Figure is provided by M. Al-Naji.

Absorbance, a. u.
Chapter 7 191
O 2
N
OH
NaBH 4
catalyst
H 2
N
t reaction
OH
250 300 350 400 450 500
Wavelength, nm
Figure 7.29. UV-vis spectra for increasing reaction time in the aqueous-phase in-situ
hydrogenation of PNP with NaBH 4 to PAP. Figure is provided by M. Al-Naji.

192 Chapter 7
7.5 Supplementary details in Outlook
Synthesis of mixed-component MOF (S1-5, [Cu3-XZnx(BTC)2-y(5-NO2-ip)y]n)
3.6 mmol of a mixture of Cu(NO3)2∙3H2O (80%, 2.88 mmol, 696 mg) and Zn(NO3)2∙6H2O
(20%, 0.72 mmol. 214 mg) was dissolved into a 15 ml solution of H2O/ethanol (1:1) in a
Teflon vessel. Subsequently, mixed-linkers (H3BTC and 5-NO2-ip) in a total molar amount
of 2 mmol (see Table 7.5 for the molar ratio differences for each sample) were added. After
the Teflon vessel was sealed in an autoclave, it was kept in the oven at 125 °C for 12h. The
resulting power product was collected by centrifuge and washed several times with
distilled water and ethanol, respectively. Subsequently, the powder was soaked in the
fresh ethanol for 24 h. After soaking the collected powder was dried under ambient
conditions and further activated by heating at 120 °C for 24 h under dynamic vacuum (ca.
10 -3 mbar).
Table 7.5. Feeding molar ratios and amounts of the linkers used in the syntheses of the S1-5.
samples
H 3 BTC : (H 3 BTC + 5-NO 2 -ipH 2 )
H 3 BTC 5-NO 2 -ipH 2
Mass
(mg)
5-NO 2 -ipH 2 : (H 3 BTC + 5-
NO 2 -ipH 2 )
Mass
(mg)
S1 90% 378 10% 42
S2 80% 336 20% 84
S3 70% 294 30% 127
S4 50% 210 50% 211
S5 0 - 100% 422
Scheme 7.4. Scheme illustration of preparation for mixed-component MOFs.

Chapter 7 193
Figure 7.30. PXRD patterns of activated mixed-component MOFs S1-4 in comparison with parent
Cu-BTC and only Zn-doped Cu/Zn-BTC.
Table 7.6. The feeding molar percentage of Zn 2+ content and defect linker 5-NO 2 -ip during the
synthesis of mixed-component sample S1-4 as well as the obtained values calculated from HPLC
and AAS results.
sample
n(Zn 2+ ): n(Zn 2+ +Cu 2+ )
n(5-NO 2 -ip): n(5-NO 2 -ip + H 3 BTC)
feeding obtained feeding obtained
S1 20% 3% 10% 3%
S2 20% 2% 20% 10%
S3 20% 2% 30% 14%
S4 20% 1% 50% 21%

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Appendix
List of Publications
Several paragraphs and figures of this thesis have already been published in peerreviewed
journals. These articles are reproduced in part with permission from the related
publishers:
Wenhua Zhang, Olesia Kozachuk, Raghavender Medishetty, Andreas Schneemann,
Ralph Wagner, Kira Khaletskaya, Konstantin Epp, and Roland A. Fischer*. “Controlled
SBU Approaches to Isoreticular Metal-Organic Framework Ruthenium-Analogues of
HKUST-1”, European Journal of Inorganic Chemistry, 2015, 2015, 3913-3920.
Wenhua Zhang, Max Kauer, Olesia Halbherr, Konstantin Epp, Penghu Guo, Miguel I.
Gonzalez, Dianne J. Xiao, Christian Wiktor, Francesc X. LIabrés i Xamena, Christof Wöll,
Yuemin Wang,* Martin Muhler, and Roland A. Fischer*. “Ruthenium Metal-Organic
Frameworks with Different Defect Types: Influence on Porosity, Sorption and Catalytic
Properties”, Chemistry-A European Journal, accepted.
Wenhua Zhang, Zhihao Chen, Majd Al-Naji, Penghu Guo, Stefan Cwik, Olesia Halbherr,
Yuemin Wang, Martin Muhler, Nicole Wilde, Roger Gläser and Roland A. Fischer*.
“Simultaneous introduction of various palladium active sites into MOF via one-pot
synthesis: Pd@[Cu3-xPdx(BTC)2]n”, Dalton Transactions (submitted).
Wenhua Zhang, Kerstin Freitag, Suttipong Wannapaiboon, Roland A. Fischer*.
“Elaboration of a Highly Porous Ru II,II analog of HKUST-1”, Inorganic Chemistry
(submitted).
Wenhua Zhang, Max Kauer, Sebastian Kunze, Stefan Cwik, Yueming Wang, and Roland
A. Fischer*. “Study of synthesis parameters on the defect engineering of HKUST-1”,
European Journal of Inorganic Chemistry (to be submitted).
Zhenlan Fang, Johannes P. Dürholt, Max Kauer, Wenhua Zhang, Charles Lochenie,
Bettina Jee, Bauke Albada, Nils Metzler-Nolte, Andreas Pöppl, Birgit Weber, Martin
Muhler, Yuemin Wang*, Rochus Schmid*, and Roland A. Fischer*. “Structural
Complexity in Metal–Organic Frameworks: Simultaneous Modification of Open Metal
Sites and Hierarchical Porosity by Systematic Doping with Defective Linkers”, Journal
of the American Chemical Society, 2014, 136, 9627-9636.

206 Appendix
List of Presentations
Wenhua Zhang, Max Kauer, Dianne J. Xiao, Ralph Wagner, Konstantin Epp, Olesia
Kozachuk, Yuemin Wang, Roland A. Fischer. “Defect Engineered” mixed valence Ru-
MOFs: study on the influence of defect metal sites.
250th American Chemical Society National Meeting & Exposition
Boston (USA), August 16 - 20, 2015, oral presentation.
Wenhua Zhang, Olesia Kozachuk, Max Kauer, Zhenlan Fang, Yuemin Wang, Roland A.
Fischer. “Defect Engineered” Mixed Valence MOFs.
4th International Conference on Metal-Organic Frameworks and Open Framework
Compounds
Kobe (Japan), September 28 - October 1, 2014, poster presentation.
Wenhua Zhang, Ralph Wagner and Roland A. Fischer. Investigation on the Ru-sites
of the ruthenium Defect-Engineered Metal-Organic Frameworks by XAS.
DELTA user meeting
Dortmund (Germany), November 2015, post presentation.

Appendix 207
Curriculum Vitae
Personal information
Name:
Wenhua Zhang
Date of Birth: 6th Dec. 1987
Place of Birth:
Nationality:
Marital Status
Education
Henan, China
Chinese
unmarried
10. 2012- Present Ruhr-University Bochum, Bochum, Germany
Ph. D. candidate at the Chair of Inorganic Chemistry II
Supervisor: Prof. Roland A. Fischer
06.2015-08.2015 University of California, Berkeley, USA
Visit Scholar in the group of Prof. Jeffrey R. Long at the
Department of Chemistry
09. 2009- 07. 2012 Zhengzhou University, Zhengzhou, China
Master of Science in Inorganic Chemistry, College of Chemistry
and Molecular Engineering
Supervisor: Prof. Guang Yang
Recommended postgraduate candidates exempt from admission
exam
09. 2005- 07. 2009 Zhengzhou University, Zhengzhou, China
Bachelor of Science in Chemistry, Department of Chemistry
Bachelor Thesis Supervisor: Prof. Guang Yang
08. 2001-06. 2005 Yichuan High School, Luoyang, China
Awards and Fellowships
High school education
2012- Present Scholarship from China Scholarship Council (CSC)

208 Appendix
05. 2015 Grant from the RS plus (Ruhr-University Bochum) for the
research (exchange) stay in the group of Prof. Jeffrey. R. Long,
University of California, Berkeley (USA) including the business
trip to ACS fall meeting 2015
02. 2015 Grant from RS Plus (RUB) for PR.INT (International Project) to
invite Dianne J. Xiao from the group of Prof. Jeffrey R. Long to
RUB
07. 2014 Grant from RS Plus (RUB) for funding the business trip to MOF
2014 conference
2009-2012 Scholarship for Outstanding Student of Zhengzhou University