An amide-based second coordination sphere promotes the dimer pathway of Mn-catalyzed CO2-to-CO reduction at low overpotential

Abstract

The [fac-Mn(bpy)(CO)3Br] complex is capable of catalyzing the electrochemical reduction of CO2to CO with high selectivity, moderate activity and large overpotential. Several attempts have been made to lower the overpotential and to enhance the catalytic activity of this complex by manipulating the second-coordination sphere of manganese and using relatively stronger acids to promote theprotonation-firstpathway. We report herein that the complex [fac-Mn(bpy-CONHMe)(CO)3(MeCN)]+([1-MeCN]+; bpy-CONHMe =N-methyl-(2,2′-bipyridine)-6-carboxamide) as a pre-catalyst could catalyze the electrochemical reduction of CO2to CO with low overpotential and high activity and selectivity. Combined experimental and computational studies reveal that the amide NH group not only decreases the overpotential of the Mn catalyst by promoting thedimerandprotonation-firstpathways in the presence of H2O but also enhances the CO2electroreduction activity by facilitating C-OH bond cleavage, making [1-MeCN]+an efficient CO2reduction pre-catalyst at low overpotential.