N-Methylation of amines is a crucial transformation for synthesizing valuable compounds. However, conventional N-methylation methods often rely on hazardous reagents. The electroreduction of CO2 as a sustainable C1 source presents an attractive alternative. Nevertheless, the direct electrochemical activation of CO2 requires high overpotentials, often leading to a low Faradaic efficiency (FE). This study presents a CO2 capture‒conversion pathway for the N-methylation of amines. High concentrations of nucleophilic piperidine preferentially capture CO2, enabling spontaneous C─N coupling, as confirmed by 13C nuclear magnetic resonance spectroscopy. Moreover, N-methyl piperidine (NMP) is produced through an electroreduction process. In situ Raman spectroscopy and theoretical calculations reveal the formation of a key piperidinium intermediate and provide insights into its role in subsequent electroreduction. This pathway effectively suppresses side reactions typical of CO2 electroreduction, achieving a high NMP FE of 71.6% at -0.6 V versus Ag/AgCl. Furthermore, the CO2 capture‒conversion pathway produces various N-methylated amines, such as dimethylamine and 1-methyl ethylenediamine, with excellent FEs, highlighting the generality and advantages of this approach.
Han et al. (Fri,) studied this question.