Repurposing First-Row Transition Metal Carbon Dioxide Reduction Electrocatalysts for Electrochemical Carboxylation of Benzyl Chloride.

Carbon dioxide (CO₂) is an abundant and useful C₁ feedstock for electrocarboxylation, a process that incorporates a carboxyl moiety into an organic molecule. In this work, three first-row transition metal CO₂ reduction electrocatalysts, NiPDI^iPr (1), NiTPA (2), and Fe(salenCl₄) (3), were explored as electrocarboxylation catalysts with benzyl chloride as a substrate. The cyclic voltammograms of all three catalysts showed current enhancements in the presence of benzyl chloride under a CO₂ atmosphere. Introduction of DMAP as additives showed further current enhancement. Electrolyses with one-compartment cell generated a moderate yield of phenylacetic acid. Addition of MgBr₂ was proven to be crucial to the formation of the carboxylate product. While the yield of carboxylation was moderate, this work showed an example of electrocarboxylation of benzyl chloride without using a metal electrode or sacrificial anode, which could lead to a more sustainable carboxylation methodology.