Phosphonium salt and ZnX2-PPh3 integrated hierarchical POPs: tailorable synthesis and highly efficient cooperative catalysis in CO2 utilization

A series of quaternary phosphonium salt and ZnX2-PPh3 integrated hierarchical porous organic polymers (POPs) with tailorable stoichiometric copolymerization proportions were obtained through the method of solvothermal synthesis. The resultant POP materials feature hierarchical porous structures, high BET surface areas (up to 1115 m2 g-1), excellent CO2 uptake abilities (87 mg g-1 at 273 K under 1 atm CO2) and multifunctional sites. Owing to the cooperative effect of quaternary phosphonium salt and homogeneously distributed ZnX2-PPh3 species, which is probably strengthened by the confined hierarchical structure and flexible frameworks, these POP catalysts provided the highest activity (initial turnover frequencies up to 6022 h-1) among heterogeneous catalysts reported to date within the context of cyclic carbonate formation. The effect of reaction parameters (reaction time, temperature, and CO2 pressure) on the catalytic performance as well as other epoxide substrates was also investigated in detail. Furthermore, these catalysts can be easily recovered and reused five times without a significant loss of activity.