Tuning Electron Localization for Mild and Selective C–N Coupling from NO and Syngas

The construction of C–N bonds typically relies on high-cost feedstocks such as ammonia, methanol, or formate under energy-intensive conditions. Here, we theoretically propose a mild, step-economical route to directly couple inexpensive nitric oxide (NO) with syngas (CO + H 2 ) into formamide (HCONH 2 ). By systematically screening low-coordination transition-metal sites confined at the edge sulfur vacancies of MoS 2 (TM-MoS 2 ), we identify Rh-, Ni-, Pt-, and Pd-MoS 2 as selective catalysts that promote C–N coupling over competing deep hydrogenation. Mechanistically, the critical N-containing intermediate is identified as HNO*, which undergoes C–N coupling with gaseous CO via an Eley–Rideal mechanism with an energy barrier around 0.60 eV, which is lower than that of the rate-limiting H 2 activation (∼0.85 eV). Electronic structure analyses reveal that the degree of electron localization on the N atom governs the coupling selectivity. On tetra-coordinated Rh, Ni, Pt, and Pd sites with relatively higher electronegativities, the early-reduction-state HNO* intermediate exhibits diminished electron localization on the N atom and weakened polarization of both N–H and N–TM bonds, kinetically facilitating the C–N coupling step. This work establishes N-site electron localization as a fundamental descriptor for selective C–N bond formation and illustrates the feasibility of edge-engineered MoS 2 in transforming waste NO and syngas into value-added formamide under mild conditions.