Electrochemical CO2 fixation with amines to synthesize α-amino acids

Abstract

α-Amino acids (α-aa) play a significant role in pharmaceutical and chemical industries. Here, we reported an electrochemical tandem system that couples the anodic dehydrogenation of amines and the cathodic carboxylation of imines. Based on a designed Lewis acid (LA)-enriched CeO₂ with indium (denoted as In-CeO_x) as cathodic electrocatalysts, we achieved 82% and 92% yields of stable imines and α-aa in a membrane-separated cell system, respectively. In a membrane-free system, quaternary or cyclic α-aa could be directly obtained from amines and CO₂ with up to 83% yield. Mechanistic investigations have elucidated that the incorporation of indium (In) yields elevated levels of LA sites. These enhanced LA sites play a pivotal role in facilitating the capture and activation of imines. This function of In-CeO_x, coupled with CO₂ activation mediated by In species, is proven to be crucial for achieving high reactivity and selectivity in the cathodic carboxylation reaction.