Hierarchical Multifunctional Ag+@Ni-BDC-NH2 Nanosheet Catalyst for the One-Pot Synergistic Catalytic Synthesis of Cyclic Carbonates

Tandem catalysis can enhance the reaction efficiency and selectivity while reducing separation and purification steps, thus improving the development of “green chemistry”. The tandem synthesis of cyclic carbonates (CCs) from olefins and CO2 is becoming one of the most promising strategies; however, designing a multifunctional catalyst with multiple sites and fast mass transfer channels to overcome mass transfer resistance at different sites remains a challenge. In this work, we controllably synthesized a bulk and nanosheet (NS) structure of Ni-BDC-NH2 (Ni-BDC-NH2 NS) via a solvent regulation strategy and successfully immobilized Ag+ in Ni-BDC-NH2 NS to form Ag+@Ni-BDC-NH2 NS, which integrated highly exposed, synergistic acid (Ag+) and base (−NH2) active sites, along with rapid mass transfer channels. Benefiting from these synergistic effects and structural advantages, Ag+@Ni-BDC-NH2 NS efficiently catalyzed one-pot synthesis of CCs from olefins and CO2, achieving 99% conversion of styrene and 51% selectivity for styrene carbonate (SC) under optimal conditions, which was significantly higher than that of contrast catalysts lacking Ag+ or –NH2 (SC selectivity <30%). Based on experiments, a feasible mechanism was proposed, in which the Lewis acid sites (Ag+) catalyzed olefin epoxidation, while the Lewis base sites (−NH2) and acid sites (Ag+) synergistically catalyzed the cycloaddition reaction of CO2 and epoxides. Additionally, the catalytic performance and structural stability were maintained even after five successive recycling tests.