Ionic liquids with multiple active sites supported by SBA-15 for catalyzing conversion of CO2 into cyclic carbonates

Synthesis of cyclic carbonates via cycloaddition reaction by means of CO2 and epoxides has been thought as an effective method for relieving global warming together with resource shortage. In order to elevate the utilization ratio of ionic liquids and separate catalysts easily after reaction, multi-site ionic liquids were designed and then immobilized on SBA-15 for the conversion of CO2 into cyclic carbonates. By combining the advantages of multiple sites and mesoporous channel, in this work, a certain amount of ionic liquids with multiple active sites were firmly immobilized on modified SBA-15. Among all the immobilized ionic liquids, [IMCA](2)Br-2@SBA-15 presented the best catalytic activity. The result showed high yield (97.4 %) and almost 100 % selectivity of propylene carbonate, which was close to equivalent molar bulk ionic liquids. This superiority could be attributed to the sufficient dispersion of multiple active sites of ionic liquids after being immobilized, enabling efficient use of ionic liquids. Furthermore, the catalyst showed good recyclability after five cycles. By characterization and DFT calculation, the synergistically catalytic mechanism based on multiple sites was proposed.