Boosting the reduction of CO2 and dimethylamine for C–N bonding to synthesize DMF via modulating the electronic structures of indium single atoms†

Abstract

The electrocatalytic reduction of CO₂ and dimethylamine (HN(CH₃)₂) for C–N coupling is a promising strategy for synthesizing N,N-dimethylformamide (DMF). However, the generation of suitable coupling intermediates via the dehydrogenation of HN(CH₃)₂ and reduction hydrogenation of CO₂ is the key challenge for achieving C–N bonding to synthesize DMF. We optimized the electronic structure of HN(CH₃)₂ and CO₂ for adsorption on indium single atoms by adjusting the coordination structure, thereby promoting the hydrogen transfer from nitrogen of dimethylamine to CO₂, which generated the intermediates of *N(CH₃)₂ and *COOH for C–N bonding to synthesize DMF. The yield of DMF synthesized on InN₃ reached 41.3 μmol L⁻¹ h⁻¹, which was about 12 times greater than that of InN₄ at −0.8 V. In situ technology and DFT calculations jointly demonstrated that compared with InN₄, InN₃ optimized the electron distribution of adsorbed CO₂ and HN(CH₃)₂. The electron density of hydrogen on HN(CH₃)₂ decreased, exhibiting its electrophilic properties. In addition, oxygen of CO₂ accumulated electrons near the dimethylamine end and exhibited strong electron-rich properties, which led to hydrogen transfer from dimethylamine to CO₂, generating the species *N(CH₃)₂ and *COOH that are conducive to C–N coupling to synthesize DMF on InN₃. This work provides important theoretical guidance for the C–N coupling of CO₂ and amines.