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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