Functional poly(ionic liquid) with unique zwitterionic structure as efficient catalyst for the conversion of ethylene...

Dimethyl carbonate (DMC) is an important chemical raw material extensively used in organic synthesis, lithium-ion battery electrolytes, etc. The primary method for industrial synthesis of DMC involves transesterification between ethylene carbonate and MeOH but faces issues with difficult catalyst separation and low catalytic activity. Based on the synergistic catalytic activity of cation and anion, this study develops poly(ionic liquid)s of [N_XPIL][PHO] and [N₃PIL][Y] with varying alkaline sites and alkalinity levels. This is accomplished by constructing functional polymer monomers containing free radical polymerization sites and nitrogen-containing alkaline groups, and by polymerizing them with suitable cross-linking monomers in a specific ratio before exchanging the resulting polymers with different anions. Results show that doping with nitrogen-containing alkaline groups leads to enhanced basic functional sites while appropriate anions provide intensified alkalinity levels. The [N₃PIL][PHO] obtained exhibits superior catalytic activity in transesterification synthesis of DMC, with a yield of 91.43% and selectivity of 99.96% at a reaction time of 2 h. The study also investigates the impact of poly(ionic liquid) cationic structure and anion types, as well as their interactions, on catalytic performance. The findings reveal that the catalytic activity of poly(ionic liquid) is restricted by the interactions between cation and anion. Based on these findings, a possible reaction mechanism was proposed, providing theoretical support for the high-efficiency production of DMC.