A Dinuclear Cobalt Cryptate as a Homogeneous Photocatalyst for Highly Selective and Efficient Visible‐Light Driven CO 2 Reduction to CO in CH 3 CN/H 2 O Solution

A dinuclear cobalt complex [Co 2 (OH)L 1 ](ClO 4 ) 3 ( 1 , L 1 =N[(CH 2 ) 2 NHCH 2 ( m ‐C 6 H 4 )CH 2 NH(CH 2 ) 2 ] 3 N) displays high selectivity and efficiency for the photocatalytic reduction of CO 2 to CO in CH 3 CN/H 2 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 Co II ions within 1 , which is strongly supported by the results of control experiments and DFT calculations.