Synthesis of Three-Dimensional Porous Porphyrin Poly(ionic liquid)s via the Menshutkin Reaction: Designing Metal-Free and Metal-Based Catalysts for Efficient Conversion of CO2 into Cyclic Carbonates

Poly(ionic liquid)s (PILs) are considered efficient and attractive heterogeneous catalysts for CO2 cycloaddition with epoxides because of the reactions that proceed without cocatalysts and solvents. Nowadays, it is widely believed that the preparation of PILs can be simply realized via common monomers by the Menshutkin reaction, but most PILs exhibit low surface areas due to the intermolecular packing. It is a challenge to obtain porous PILs with diverse functional groups that can activate substrates. In this contribution, we utilized the Menshutkin-type reaction with three-dimensional contorted monomers to manufacture a new kind of porphyrin-functionalized microporous PIL for the first time. It is worth noting that metal-free PILs containing porphyrin, imidazole, and imidazolium active groups can promote CO2 activation and achieve CO2 cycloadditions under relatively mild conditions. After metalation, their catalytic activities have been enhanced significantly under more moderate conditions. Moreover, both metal-free and metal-based PILs can be recycled at least six times without any obvious decrease in catalytic activity. Finally, the apparent activated energies are calculated from the kinetic study to demonstrate the possible reaction mechanism. This work not only provides an efficient strategy for constructing porous PILs by designing functional monomers but also highlights a promising method for activating and converting CO2 into fine chemicals under mild conditions.