A Bio‐inspired Cu 4 O 4 Cubane: Effective Molecular Catalysts for Electrocatalytic Water Oxidation in Aqueous Solution

Inspired by the cubic Mn 4 CaO 5 cluster of natural oxygen‐evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts, especially M 4 O 4 cubane‐like clusters (M=transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M 4 O 4 clusters, however, copper‐based molecular catalysts are poorly understood. Now, bio‐inspired Cu 4 O 4 cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with a turnover frequency (TOF) of 267 s −1 for [(L Gly ‐Cu) 4 ] at 1.70 V and 105 s −1 for [(L Glu ‐Cu) 4 ] at 1.56 V. Electrochemical and spectroscopic study revealed a successive two‐electron transfer process in the Cu 4 O 4 cubanes to form high‐valent Cu III and Cu III O . intermediates during the catalysis.