Carbene Ligands Enabled C-N Coupling for Methylamine Electrosynthesis: A Computational Study

Abstract

Electrocatalytic conversion of carbon monoxide (CO) and nitric oxide (NO) into methylamine (MMA, CH₃NH₂) could convert excessive renewable energy and environmental pollutants into valuable chemicals. The main hurdle, however, is the inefficient C−N coupling as a result of the repulsive dipole− dipole interaction between adjacent coupling precursors. Herein, we report a simple strategy to weaken the repulsive dipole−dipole interaction using N-heterocyclic carbene to modify the pristine catalyst surface. The pristine catalyst for our study is MXene-doped with two Cu atoms using the O vacancy site of Mo₂NO₂ (Cu₂@v- Mo₂NO₂). Our molecular modeling work based on density functional theory calculation discovered that surface-functionalized carbene ligands perturb the electronic configuration of chelated Cu sites, hence causing charge redistribution on the adsorbed reaction intermediates. Such charge redistribution successfully weakens the CO/NO dipole−dipole repulsion, effectively optimizes the binding strength of precursors, and leads to an effective C−N bond formation. Consequently, a pathway that selectively converts CO and NO to MMA with a facile C−N coupling step and low limiting potential is identified on the catalyst surface. Our work suggests a facile electrocatalyst surface functionalization strategy for the improved coupling between small-molecule precursors featuring dipole−dipole repulsion, with the potential to generalize to the sustainable synthesis of multi-carbon/nitrogen chemicals.