Bio-inspired benzimidazole-functionalized manganese terpyridine complexes for electrochemical CO2 reduction

Inspired by the active site of carbon monoxide dehydrogenase (CODH), where a pair of amino acids facilitating hydrogen bonding manages the reversible interconversion of CO and CO2 with high efficiency, we developed a family of manganese terpyridine derivatives (1-4), in which a benzimidazole moiety functions as a proton relay to assist the CO2 reduction reaction (CO2RR). To regulate the position of the proton donor, the benzimidazole moiety was introduced into the framework by two approaches, and the pK a of the proton relay was adjusted by methylation of the benzimidazole moiety. We found that all such designs led to a sharp corruption in the activity of electrochemical CO2 reduction compared with that of our previously reported analogues. The corruption was ascribed to the pK a of the benzimidazole moiety, which resulted in inefficient proton exchange.