Synergistic Effect Promotes Visible‐Light–Driven CO2‐To‐CO Conversion by Macrocyclic Dinuclear Mixed‐Valence Co (II)/Co (III) Complexes

ABSTRACT The catalytic conversion of carbon dioxide (CO 2 ) into valuable energy under light sources is one of the effective ways to achieve carbon cycle. The reported nonprecious metal complex catalysts still show the shortcomings of low catalytic activity and low selectivity in visible‐light–driven CO 2 reduction, especially in aqueous systems. Herein, we report three dinuclear mixed‐valence Co (II)/Co (III) complexes 1 – 3 bearing macrocyclic ligands that exhibit high activity and selectivity for visible‐light–driven photocatalytic CO 2 reduction in an aqueous system. Moreover, the TON CO and CO selectivity for macrocyclic dinuclear mixed‐valence complex 3 reach as high as 4100 and 96%, respectively, which is about 4.9 times higher than that of mononuclear Co (II) complex 4 . Through electrochemical and DFT calculations, we found that the increase in photocatalytic activity of 3 is due to the synergistic effect between the two metal centers, in which one Co site stabilizes the *COOH intermediate and reduces the energy barrier of the rate‐determining step, thereby increasing the catalytic activity.