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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).