Metal–Ligand Exchange Coupling Promotes Iron-Catalyzed Electrochemical CO2 Reduction at Low Overpotentials

Biological and heterogenous catalysts for electrochemical CO2 reduction often exhibit a high degree of electronic delocalization that serves to minimize overpotential and maximize selectivity over hydrogen evolution. Here, we report a molecular iron(II) complex that achieves a similar feat as a result of strong metal–ligand exchange coupling. This interaction promotes an open-shell singlet electronic structure that drives the electrochemical reduction of CO2 to CO with over 90% selectivity and turnover frequencies of 100,000 s−1 at low overpotentials, with no degradation over 20 hours. The decrease in the thermodynamic barrier engendered by this strong metal–ligand exchange coupling enables homogeneous CO2 reduction catalysis in water without compromising reaction selectivity.