Water Oxidation Catalyst <i>cis-</i>[Ru(bpy)(5,5′-dcbpy)(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup> and Its Stabilization in Metal–Organic Framework
Roman Ezhov, Alireza Karbakhsh Ravari, Allison Page, Yulia Pushkar
Abstract
The realization of artificial photosynthesis requires the design of fast and durable water oxidation catalysts that can be incorporated into future sunlight-to-chemical-fuels assemblies. Here we report on the simple and readily synthetically accessible cis-[Ru(bpy)(5,5′-dcbpy)(H2O)2]2+ (1) (bpy = 2,2′-bipyridine, 5,5′-dcbpy = 2,2′-bipyridine-5,5′-dicarboxylic acid) water oxidation catalyst. Its O2 evolution has first-order dependence on the catalyst following the water nucleophilic attack mechanism. The cis-[RuV═O,–OH(bpy)(5,5′-dcbpy)]2+ intermediate was detected in the reaction mixtures by X-ray absorption and resonance Raman spectroscopy in agreement with the proposed mechanism and DFT calculations. To avoid a deactivating dimerization, the catalyst was postsynthetically incorporated into the UIO-67 metal–organic framework with retention of water oxidation activity. Similar results were obtained via the incorporation of cis-[Ru(bpy)(5,5′-dcbpy)]Cl2, a chemical precursor of 1, to UIO-67 followed by hydrolysis. Postsynthetic doping of the UIO-67 thin film on a FTO glass electrode with 1 leads to an increase of the catalytic current by two orders of magnitude. Thus, [Ru(bpy)(5,5′-dcbpy)(H2O)2]2+–UIO-67 is a promising building block for integrated photosynthetic systems.