Efficient fixation of CO2 to cyclic carbonate using hydroxyl-functionalized protic ionic liquids with multiple ion pairs under mild conditions

Abstract

The development of catalysts with high stability, easy recovery, and multiple active sites is a particularly challenging aspect of CO₂ catalysis. In this study, several hydroxyl-functionalized ionic liquids (HPILs) with multiple active sites were developed to achieve efficient CO₂ conversion from flue gas. We investigated the cycloaddition performance with CO₂ using these HPILs as catalysts and allyl glycidyl ethers (AGE) as model substrates. Among these, the [TDMPH]I catalysts, featuring I⁻ and hydroxyl active sites, achieved impressive product yields (98 %) and selectivity (>99 %) at 60 °C, 1 bar, and 5 mol% catalyst dosage over 4 h. Notably, this reaction was conducted under solvent-free conditions without the need for co-catalysts. Furthermore, these ionic liquids exhibit non-homogeneous catalyst characteristics, enabling efficient recovery via ethyl acetate crystallization, along with excellent cyclic stability and high activity.