Water Oxidation Catalyst cis-[Ru(bpy)(5,5′-dcbpy)(H2O)2]2+ and Its Stabilization in Metal-Organic Framework

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 O-2 evolution has first-order dependence on the catalyst following the water nucleophilic attack mechanism. The cis-[Ru-V = 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)]Cl-2, 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.