Co-electrocatalytic CO2 reduction mediated by a dibenzophosphole oxide and a chromium complex

Abstract

We report a co-electrocatalytic system for the selective reduction of CO₂ to CO, comprised of a previously reported molecular Cr complex and 5-phenylbenzo[b]phosphindole-5-oxide (PhBPO) as a redox mediator. Under protic conditions, the co-electrocatalytic system attains a turnover frequency (TOF) of 15 s⁻¹ and quantitative selectivity for CO. It is proposed that PhBPO interacts with the Cr-based catalyst, coordinating in an axial position trans to an intermediate hydroxycarbonyl species, M–CO₂H, mediating electron transfer to the catalyst and lowering the barrier for C–OH bond cleavage.