Electrochemical Upgradation of C n to C n +1 ( n = 1, 2, 3, 4...) Alcohol via C–C Coupling on Cobalt Phenanth

Abstract

Carbon–carbon (C–C) coupling reactions are crucial in modern synthetic chemistry due to their central role in construction of complex organic molecules. Herein, density functional theory (DFT) calculations were performed to explore the detailed mechanistic pathway for the electrochemical upgradation of CnOH to Cn+1OH (n = 1, 2, 3, 4...) through the C–C coupling of CO and CnOH on the Co(Phen)2 catalyst complex. The most favorable pathway as predicted from our DFT calculation is *→*CO→CO*CnH2n+1→*COCnH2n+1→*OCHCnH2n+1→*OCH2CnH2n+1→CnH2n+1CH2OH (n = 1, 2, 3, 4...). The *OCHCnH2n+1→*OCH2CnH2n+1 step is the most thermodynamically uphill step for this electrochemical conversion process. The C–C coupling reaction is enabled by the large open space at the Co active site provided the perpendicularly oriented phenanthroline ligands that facilitates the simultaneous adsorption of CO and alcohol fragment at the active site. Our results indicate that Co(Phen)2 complex can be employed as an effective electrocatalyst for the upgradation of lower alcohols to higher alcohols with high product selectivity and low overpotential. Such an electrocatalyst will enable the use of CO for production of long-chain hydrocarbons, promoting the development of sustainable air fuels.