Building a Co-Salen-Immobilized Porous Organic Polymer Catalyst for CO₂ Cycloaddition

The CO₂-epoxide addition to cyclic carbonate is of great significance but usually requires high temperatures and CO₂ pressures. Herein, a spirobifluorene-based porous organic polymer catalyst is designed with a Co-salen complex immobilized on the backbone (ST-CoSalen-POP) to enable CO₂ fixation under mild conditions. ST-CoSalen-POP possesses a high Co-loading content (9.35 wt%), a large pore volume, and high CO₂ adsorption capacity. This catalyst achieves a 96% yield in the cycloaddition of CO₂ with epoxides at 25 °C and 0.1 MPa CO₂ pressures. Moreover, ST-CoSalen-POP also offers the advantages of wide adaptability over epoxide substrates and high structural stability for three consecutive cycles. This study presents a novel catalytic approach for promoting CO₂ fixation, offering a significant advancement in the efficient synthesis of fine chemicals.