High‐Performance and Recyclable Multisite Catalytic System for CO₂ Fixation Using Crown Ether‐Linked Schiff Base and Alkali Halides

The development of efficient and sustainable catalytic systems for CO₂ fixation is crucial for carbon‐neutral chemical processes. We now report a high‐performance and recyclable multisite catalytic system based on a crown ether‐linked Schiff base in combination with alkali halides for the synthesis of cyclic carbonates from epoxides and CO₂. The designed catalyst features multiple active sites, including a Lewis acidic alkali ion center and a nucleophilic iodide source, enabling the efficient activation of epoxides under solvent‐free conditions with atmospheric pressure. Systematic studies on the effects of cations and calcium salts revealed that the multi‐activation mechanism plays a critical role in enhancing the catalytic performance. The catalyst exhibited a high selectivity and activity, achieving up to a 97 % yield of cyclic carbonates at atmospheric CO₂ pressure and 70 °C. The simulated post‐combustion exhaust gas (CO₂: 7.5 %, N₂: 92.5 %, relative humidity: 90 %) was concentrated to 97 % and used as the material for the reaction to yield 90 % of styrene carbonate from styrene oxide. Furthermore, the catalyst was easily recovered and reused for multiple cycles without any significant loss of activity. This study provides a practical and environmentally‐friendly approach for CO₂ utilization, contributing to the advancement of sustainable catalytic processes.