Crown Ether-based Hypercrosslinked Polymers for the Cycloaddition of CO₂ with Epoxides

The cycloaddition reaction of CO₂ with epoxides to produce cyclic carbonates is one of the effective ways of CO₂ resource utilization, but the traditional catalysts used in industry often have some disadvantages such as harsh reaction conditions and difficult recycling of catalysts. The development of heterogeneous catalysts that enable cycloaddition reactions to occur under mild conditions remains a major challenge. The hypercrosslinked polymer (HCPs) obtained by Friedel-Crafts alkylation reaction is a three-dimensional network with permanent porosity, which has great application potential in the catalytic conversion of CO₂. In this research, a kind of crown ether-based hypercrosslinked polymer has been designed and synthesized and successfully used in the CO₂ cycloaddition reaction. When two industrial catalysts (potassium iodide or tetrabutylammonium bromide) were used as co-catalysts, a series of cyclic carbonates have been synthesized efficiently under relatively mild and solvent-free conditions, showing good cyclic stability and substrate generality. In KI/CE-HCP-1 two-component catalytic system, the conversion rate of epichlorohydrin can reach more than 90% under 100 ℃ and 1.0 MPa CO₂ pressure for 16 h. Therefore, the construction of this efficient two-component co-catalytic system provides a good path for the resource utilization of CO₂ under mild conditions.