A low-nuclear Ag₄ nanocluster as a customized catalyst for the cyclization of propargylamine with CO₂

The preparation of 2-Oxazolidinones using CO2 offers opportunities for green chemistry, but multi-site activation is difficult for most catalysts. Here, A low-nuclear Ag-4 catalytic system is successfully customized, which solves the simultaneous activation of acetylene (-C equivalent to C) and amino (-NH-) and realizes the cyclization of propargylamine with CO2 under mild conditions. As expected, the Turnover Number (TON) and Turnover Frequency (TOF) values of the Ag4 nanocluster (NC) are higher than most of reported catalysts. The Ag4* NC intermediates are isolated and confirmed their structures by Electrospray ionization (ESI) and 1H Nuclear Magnetic Resonance (H-1 NMR). Additionally, the key role of multiple Ag atoms revealed the feasibility and importance of low-nuclear catalysts at the atomic level, confirming the reaction pathways that are inaccessible to the Ag single-atom catalyst and Ag-2 NC. Importantly, the nanocomposite achieves multiple recoveries and gram scale product acquisition. These results provide guidance for the design of more efficient and targeted catalytic materials.