Cross-linked polymer grafted with functionalized ionic liquid as reusable and efficient catalyst for the cycloaddition of carbon dioxide to epoxides

A series of cross-linked polydivinylbenzene polymers covalently grafted with various (hydroxyl, carboxyl, and amino) functional ionic liquid were fabricated by a simple method and evaluated as heterogeneous catalysts for the synthesis of cyclic carbonates from CO₂ and epoxides. The as-fabricated catalysts show good performance across a wide range of epoxides in the absence of solvent and co-catalyst, especially the one that was grafted with hydroxyl ionic liquid. The effects of functional groups in ionic liquid, reaction temperature, initial CO₂ pressure, and reaction time on the cycloaddition reaction were investigated. It is suggested that synergetic effect between functional groups and bromide ions facilitates the catalytic reaction. It is noted that the hydroxyl group with moderate hydrogen bonding is more crucial for the cycloaddition reaction than the other groups. In addition, the recycling test showed that the catalyst could be reused for as many as six times without any loss of catalytic activity.