A Dinuclear Cobalt Cryptate as a Homogeneous Photocatalyst for Highly Selective and Efficient Visible-Light Driven CO2 Reduction to CO in CH3CN/H2O Solution

A dinuclear cobalt complex [Co-2](OH)L-1](ClO4)(3) (1, L1 = N[(CH2])(2)NHCH2(m-C6H4)CH2NH(CH2)(2)](3)N) displays high selectivity and efficiency for the photocatalytic reduction of CO2 to CO in CH3CN/H2O (v/v= 4:1) under a 450 nm LED light irradiation, with a light intensity of 100 mWcm(-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 Co-II ions within 1, which is strongly supported by the results of control experiments and DFT calculations.