Room-Temperature CO Oxidative Coupling for Oxamide Production over Interfacial Au/ZnO Catalysts

The conversion of carbon monoxide (CO) into high-value organic molecules has long been pursued by both industry and academia. One of the central challenges is to realize carbon-carbon coupling with high selectivity for CO insertion. We report here a highly selective Au/ ZnO composite catalyst for one-step oxidative coupling of CO with secondary amines, producing oxamides. The reaction is >99% selective under ambient conditions, which exhibits a subtle change of catalyst activity over similar to 120 h in a fixed-bed reactor. A combination of microscopic and spectroscopic studies (including X-ray photoemission spectroscopy, X-ray absorption spectroscopy, CO-Fourier transform infrared spectroscopy, and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy) and machine learning reveal that the active site is the Au-ZnO interface with a Au nanocluster attached to the ZnO support via nonstoichiometric ZnOx (x > 1) linkages. The reaction mechanism and key reaction intermediates were confirmed by density functional theory calculations and in situ diffused reflectance infrared Fourier transform spectroscopy signals. Our results open an avenue in heterogeneous catalysis to achieve the ambient-condition CO transformation by exploiting the interfacial synergistic effects.