Bioinspired Binickel Catalyst for Carbon Dioxide Reduction: The Importance of Metal-ligand Cooperation

Catalyst design for the efficient CO₂ reduction reaction (CO₂RR) remains a crucial challenge for the conversion of CO₂ to fuels. Natural Ni-Fe carbon monoxide dehydrogenase (NiFe-CODH) achieves reversible conversion of CO₂ and CO at nearly thermodynamic equilibrium potential, which provides a template for developing CO₂RR catalysts. However, compared with the natural enzyme, most biomimetic synthetic Ni-Fe complexes exhibit negligible CO₂RR catalytic activities, which emphasizes the significance of effective bimetallic cooperation for CO₂ activation. Enlightened by bimetallic synergy, we herein report a dinickel complex, Ni^IINi^II(bphpp)(AcO)₂ (where NiNi(bphpp) is derived from H₂bphpp = 2,9-bis(5-tert-butyl-2-hydroxy-3-pyridylphenyl)-1,10-phenanthroline) for electrocatalytic reduction of CO₂ to CO, which exhibits a remarkable reactivity approximately 5 times higher than that of the mononuclear Ni catalyst. Electrochemical and computational studies have revealed that the redox-active phenanthroline moiety effectively modulates the electron injection and transfer akin to the [Fe₃S₄] cluster in NiFe-CODH, and the secondary Ni site facilitates the C-O bond activation and cleavage through electron mediation and Lewis acid characteristics. Our work underscores the significant role of bimetallic cooperation in CO₂ reduction catalysis and provides valuable guidance for the rational design of CO₂RR catalysts.