2.2. Preparation of POM–IL catalysts
For the preparation of QPS cation, isoquinoline (0.11 mol) and 1,3-propanesultone (0.10 mol) were dissolved in toluene (30 mL) and stirred at 40 °C for 72 h under nitrogen atmosphere. A white precipitate (QPS) was formed. It was filtered, washed with diethyl ether
three times and dried in vacuum.
For the preparation of [QPS]PW, QPS (0.06 mol) was added to an aqueous solution of PW (0.02 mol, 5 mL), and then the mixture was stirred at room temperature for 24 h. Water was removed in vacuum to give the final product as a solid. [PyPS]PW, [TMAPS]PW, and [MIMPS]PW were synthesized according to our previously published paper [27].