A Dinuclear Cobalt Cryptate as a Homogeneous Photocatalyst for Highly Selective and Efficient Visible-Light Driven CO2 Reduction to CO in CH3 CN/H2 O Solution.

A dinuclear cobalt complex [Co2 (OH)L1 ](ClO4 )3 (1, L1 =N[(CH2 )2 NHCH2 (m-C6 H4 )CH2 NH(CH2 )2 ]3 N) displays high selectivity and efficiency for the photocatalytic reduction of CO2 to CO in CH3 CN/H2 O (v/v=4:1) under a 450 nm LED light irradiation, with a light intensity of 100 mW cm-2 . The selectivity reaches as high as 98 %, and the turnover numbers (TON) and turnover frequencies (TOF) reach as high as 16896 and 0.47 s-1 , respectively, with the calculated quantum yield of 0.04 %. Such high activity can be attributed to the synergistic catalysis effect between two CoII ions within 1, which is strongly supported by the results of control experiments and DFT calculations.