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 Ag₄ catalytic system is successfully customized, which solves the simultaneous activation of acetylene (-C≡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 (¹H 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 Ag₂ 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.