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

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.