Benzyl bromide and methylimidazolium were added at a molar ratio of 1.1:1 to a round-bottom flask equipped with a magnetic stirrer, heating device, and condenser. The mixture was stirred and reacted at 60–90 °C for 8 h. After cooling, the supernatant was discarded, and the mixture was washed twice with ethyl acetate. The mixture was then cured in a refrigerator for 12 h. The cured product was dissolved in water and then subjected to ion exchange with ammonium hexafluorophosphate at a molar ratio of 1:1.2 at room temperature. After the exchange was completed, the product was filtered, washed with water and petroleum ether, and dried in a vacuum oven for later use.
