CO2 conversion into carbonate using pyridinium-based ionic liquids under mild conditions

A sequence of pyridinium-based acidic-ionic liquids (PyAILs) as dual-functional ILs were synthesized and applied as metal-free, stable and homogeneous catalysts to convert economical, renewable, sustainable and inert CO2 into carbonates. These PyAILs were used to synthesize high-efficiency terminal carbonate from epoxide and greenhouse CO2. Various factors that affected the conversion and selectivity of the reaction including the amount of catalyst, chain length of acidic pendant, anion type, reaction temperature, solvent and reaction time were investigated. The special design of the dual acid-functionalized PyAILs, activated CO2 and epoxide, and the reaction was carried out under mild conditions, solvent-free, low pressure with great TOF and excellent con-version and selectivity above 99% for different types of terminal epoxides. A conceivable reaction mechanism was proposed and it was signified that the carboxylic group and halide ions had a synergetic effect on cyclic carbonates synthesis. In addition, PyAILs can be easily separated by simple extraction from the reaction medium.