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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