Robust Tertiary Amine Suspended HCIPs for Catalytic Conversion of CO₂ into Cyclic Carbonates under Mild Conditions

A series of tertiary amine suspended hyper-cross-linked ionic polymers (HCIPs), characterized by a rich mesoporous structure, high ionic liquid (IL) density, and good CO₂ adsorption capability, were readily prepared via a postsynthetic method. The self-polymerization of 1,3,5-tris(bromomethyl) benzene (TBB) or its copolymerization with 4,4'-bis(bromomethyl) biphenyl (BBP) in varying ratios, followed by grafting with N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA), yielded the target TMPDA-HCIPs. These HCIPs constitute one of the limited categories of heterogeneous water-tolerant catalyst types ever developed for the cycloaddition reaction between CO₂ and epoxides. Specifically, chloropropylene carbonate (CPC) was produced in 99.9% yield with 99% selectivity at 80 °C and 1 bar of CO₂ pressure in the presence of 22 mol % water relative to the epoxide substrate. Furthermore, when simulated flue gas served as the CO₂ source, the same ratio of water enhanced the CPC yield from 81.9% to 91.5% under 1 MPa pressure, with the selectivity only slightly decreasing from 99% to 94.1%. Additionally, the catalyst could be easily recovered and maintained a high catalytic performance after six cycles. In conclusion, this study presents a robust water-tolerant heterogeneous catalyst for the efficient synthesis of cyclic carbonates from CO₂ under mild conditions, potentially reducing the high costs of purifying real flue gas that contains water vapor.