Electrochemical Water Oxidation by a Catalyst-Modified Metal-Organic Framework Thin Film

Water oxidation, a key component in artificial photosynthesis, requires high overpotentials and exhibits slow reaction kinetics that necessitates the use of stable and efficient heterogeneous water-oxidation catalysts (WOCs). Here, we report the synthesis of UiO-67 metal-organic framework (MOF) thin films doped with [Ru(tpy)(dcbpy)OH2](2+) (tpy= 2,2':6', 2''-terpyridine, dcbpy = 5,5'-dicarboxy-2,2'-bipyridine) on conducting surfaces and their propensity for electrochemical water oxidation. The electrocatalyst oxidized water with a turnover frequency (TOF) of 0.2 +/- 0.1) s(-1) at 1.71 V versus the normal hydrogen electrode (NHE) in buffered solution (pH similar to 7) and exhibited structural and electrochemical stability. The electroactive sites were distributed throughout the MOF thin film on the basis of scan-ratedependent voltammetry studies. This work demonstrates a promising way to immobilize large concentrations of electroactive WOCs into a highly robust MOF scaffold and paves the way for future photoelectrochemical water-splitting systems.