Protic ionic liquids tailored by different cationic structures for efficient chemical fixation of diluted and waste CO2 into cyclic carbonates

Environment-friendly approaches to directly convert atmospheric or flue gas CO2 to high-value chemicals is of great significance yet challenging. Protic ionic liquid catalysts with excellent properties are showing potential for the chemical fixation of CO2. In this work, a series of protic ionic liquids with different cationic structures have been synthesized, which bear hydrogen-bond interactions between unique N+-H bonds and the O atoms of epoxides and they are highly active catalytic sites. It was found that [AlTMG]Br shows obviously high/good catalytic activity for converting epoxides into cyclic carbonates with CO2 in the atmosphere or at even lower pressures (15% CO2 and 85% N-2), outperforming the corresponding homogeneous catalyst analogues and superior to the known solvent- and metal-free catalytic systems. The results showed that under mild homogeneous catalytic reaction conditions, low-pressure CO2 can directly react with epoxides to give cyclic carbonates with excellent yields, without any co-catalysts such as metals, solvents and additives. In addition, the best catalyst [AlTMG]Br was proved to be robust with remarkable reusability, and displaying great potential for pollution reduction and industrial applications for the chemical conversion of atmospheric CO2.

Automated summary

Protic ionic liquid catalysts have been synthesized for the chemical fixation of CO2, with [AlTMG]Br showing high catalytic activity for converting epoxides into cyclic carbonates under mild reaction conditions. These catalysts outperform corresponding homogeneous catalyst analogues and offer potential for pollution reduction and industrial applications.