Integrating Homogeneous and Heterogeneous Catalysis in a Copper Nanocluster with Lewis Acid-Base Sites for Chemical Conversion of CO2 and Propargylamine

It remains a significant challenge to develop a catalyst that merges the advantages of homogeneous and heterogeneous catalysis with high reactivity and great recyclability. Herein, an atomically precise Cu-6-NH2 nanocluster with distorted octahedral Cu-6 core and NH2-functionalized ligands has been developed as the first homo/heterogeneous catalyst to catalyze the cyclization reaction of propargylic amines with carbon dioxide (CO2) under mild conditions. As a homogeneous catalyst, Cu-6-NH2 shows excellent catalytic activity with high turnover frequency due to highly accessible active sites. The definite coordination geometry and homogeneity nature of active centers make it convenient to investigate the structure-activity relationship at the atomic level through experiments and theory calculations. In addition, the nanocluster exhibits excellent stability, great recrystallizability, and reusability in five catalytic cycles, in which its catalytic performance has no obvious decrease. Moreover, Cu-6-NH2 incorporates Lewis acid and base sites in metal and ligand, respectively, which can promote catalytic efficiency in a synergistic effect in the absence of any cocatalysts. Importantly, Cu-6-NH2 can realize direct conversion of CO2 in simulated flue gas into oxazolidinones with high efficiency. The metal-ligand cooperative effect and integrated advantages of homogeneous and heterogeneous catalysis would provide new perspectives to achieve advanced metal nanocluster catalysts for CO2 conversion.