Efficient CO2 fixation under ambient pressure using poly(ionic liquid)-based heterogeneous catalysts
We report the use of ionic liquid based polymers for the conversion of epoxides into cyclic carbonates under ambient pressure (1.02 atm). The polymeric catalysts were prepared via thiol–ene click chemistry using trithiocyanuric acid (TTCA) and divinyl imidazolium-based ionic liquids in the presence of AIBN as a radical initiator under thermal conditions. TTCA acts as a planar C3 symmetric thiol molecule and helps in CO2 absorption due to the presence of a triazine moiety. Additionally, TTCA helps to achieve the optimum separation of catalytically active sites i.e. imidazolium bromide moieties. The resulting poly(ionic liquid) together with KI as a co-catalyst has been found to be very efficient for the conversion of a wide number of epoxide substrates into their corresponding cyclic carbonates under CO2 filled balloon conditions. The catalyst was able to retain its activity up to 6 cycles.