The solar-driven CO 2 reduction is achallenge in the field of "artificial photosynthesis", as most catalysts display low activity and selectivity for CO 2 reduction in watercontaining reaction systems as ar esult of competitive proton reduction. Herein, we report ad inuclear heterometallic complex, [CoZn(OH)L 1 ](ClO 4 ) 3 (CoZn), which shows extremely high photocatalytic activity and selectivity for CO 2 reduction in water/acetonitrile solution. It achieves aselectivity of 98 %for CO 2 -to-CO conversion, with TONa nd TOFv alues of 65000 and 1.8 s À1 ,r espectively,4 ,1 9, and 45-fold higher than the values of corresponding dinuclear homometallic [CoCo-(OH)L 1 ](ClO 4 ) 3 (CoCo), [ZnZn(OH)L 1 ](ClO 4 ) 3 (ZnZn), and mononuclear [CoL 2 (CH 3 CN)](ClO 4 ) 2 (Co), respectively, under the same conditions.T he increased photocatalytic performance of CoZn is due to the enhanced dinuclear metal synergistic catalysis (DMSC) effect between Zn II and Co II , which dramatically lowers the activation barriers of both transition states of CO 2 reduction.