Breaking the activity-selectivity trade-off in CO 2 -driven N-monomethylation on a bifunctional inverse ZrZnO x /Cu catalyst

Abstract 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 ZrZnOx/Cu catalyst in which Zr-O-Zn interfacial sites enable high-yield N-monomethylation under mild conditions. The optimized catalyst delivers a 93% N-methylaniline yield 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.