Abstract:
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Incorporating molecular catalysts into metal–organic frameworks (MOFs) is a promising strategy for
improving their catalytic longevity and recyclability. In this article, we investigate and compare synthetic
routes for the incorporation of the potent water oxidation catalyst Ru(tda)(pyCO2H)2 (tda = 2,2’:6’,2’’-terpyridine-
6,6’’-dicarboxylic acid, pyCO2H = iso-nicotinic acid) as a structural linker into a Zr-based UiOtype
MOF. The task is challenging with this particular metallo-linker because of the equatorial dangling
carboxylates that can potentially compete for Zr-coordination, as well as free rotation of the pyCO2H
groups around the HO2Cpy⋯Ru⋯pyCO2H axis. As a consequence, all attempts to synthesize a MOF with
the metallo-linker directly under solvothermal conditions led to amorphous materials with the Ru(tda)
(pyCO2H)2 linker coordinating to the Zr nodes in ill-defined ways, resulting in multiple waves in the cyclic
voltammograms of the solvothermally obtained materials. On the other hand, an indirect post-synthetic
approach in which the Ru(tda)(pyCO2H)2 linker is introduced into a preformed edba-MOF (edba = ethyne
dibenzoic acid) of UiO topology results in the formation of the desired material. Interestingly, two distinctly
different morphologies of the parent edba-MOF have been discovered, and the impact that the
morphological difference has on linker incorporation is investigated |