A bioinspired molybdenum-copper molecular catalyst for CO2 electroreduction

Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO2 to formate catalyzed by the bimetallic complex [(bdt)Mo-VI(O)(S2CuCN)-C-I](2-) (bdt = benzenedithiolate), a mimic of the active site of the Mo-Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO2. We found that the two-electron reduction of [(bdt)Mo-VI(O)(S2CuCN)-C-I](2-) triggers the transfer of the oxo moiety to CO2 forming CO32- and the complex [(bdt)(MoS2CuCN)-S-IV-C-I](2-) and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive (MoH)-H-V hydride intermediate which reacts with CO2 to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.