Boosting photocatalytic CO₂-to-CO conversion using a biomimetic dinuclear Co(II) complex through an HCO₃⁻-mediated pathway

Dinuclear metal synergistic catalysis (DMSC) has been evidenced to be effective in enhancing the catalytic activity for CO₂ reduction. However, the reaction kinetics of CO₂ reduction is still limited by the local CO₂ concentration around the dinuclear catalytic centers. Inspired by the structure of carbonic anhydrase, we have designed and synthesized a dinuclear cobalt(II) complex with an –OH group. This complex not only exhibits DMSC for CO₂ reduction but also possesses excellent capture capacity for CO₂ molecules. Consequently, the complex demonstrates high efficiency for the photocatalytic reduction of CO₂ to CO, with turnover number reaching as high as 43,400 and a selectivity of 97%. Even in 10% CO₂, the complex still shows state-of-the-art catalytic activity. The results of experiments and theoretical calculations reveal that besides the DMSC contributing to the enhanced catalytic activity, the –OH group in the dinuclear cobalt(II) complex facilitates the capture of CO₂ by the formation of HCO₃⁻ intermediates, thereby enhancing the affinity towards CO₂ and boosting the catalytic activity for CO₂-to-CO conversion.