Insight into the catalytic activity for a series of synthesized and newly designed phosphonium-based ionic liquids on the fixation of carbon dioxide

Various catalysts have been explored for the coupling reaction of carbon dioxide with propylene oxide in the past decade. However, the search for high-efficiency single-component catalyst in the absence of metal and solvent is still a challenging issue. In this work, the catalytic activity of a series of functionalized phosphonium-based ionic liquids (FPBILs) is investigated by density functional theory. The influences of functional group, chain length of cation, and anion on the catalytic performance have been explored. The carboxyl-functionalized FPBIL with the moderate alkyl chain length presents the best catalytic activity among all investigated catalysts. On the basis of above information, a new sulfonyl hydroxide-functionalized FPBIL is designed. Moreover, its catalytic activity is theoretically examined as compared with that of carboxyl-functionalized FPBIL.