Breaking the activity–selectivity trade-off in CO₂-driven N-monomethylation on a bifunctional inverse ZrZnO_x/Cu catalyst

Selective N-methylation utilizing CO₂ as a renewable C1 source offers a sustainable route to valuable amines, yet arresting the reaction at the N-monomethylation stage remains a formidable challenge. Here, we report an inverse ZrZnO_x/Cu catalyst in which Zr–O–Zn interfacial sites enable high-yield N-monomethylation under mild conditions. The optimized catalyst delivers an N-methylaniline yield of 93% at near-full aniline conversion under 150 °C and 3 MPa, outperforming binary ZrO₂/Cu and commercial Cu/ZnO/Al₂O₃ catalysts. The catalyst also exhibits robust stability over ten consecutive cycles and good applicability across diverse primary amines. Mechanistic studies reveal that the bifunctional interface provides adjacent Lewis acid and basic/defect sites, stabilizes CO₂-derived oxygenated intermediates, and suppresses N-methylaniline re-adsorption and subsequent over-methylation, thereby decoupling the competing methylation steps. This work proposes a bifunctional mechanism that integrates site-blocking effects with intermediate stabilization, providing a highly efficient and stable protocol for precise C–N bond formation.