A Water-Lean Triazole Ionic Liquid Biphasic Solvent for Energy-Efficient CO2 Capture Through Reversible Polarity and Intermolecular Hydrogen Bonding

The development of novel functionalized solvents with low volatility, high mass capacity, and low energy consumption for CO2 capture technology is still a significant challenge. In this study, two triazole-functionalized ionic liquids (TFILs) were designed and combined with imidazole organic solvents as phase separation agents to form novel biphasic solvents for CO2 capture. When the mass ratio of [N2222][1,2,4-Triz]/1-methylimidazole (N-MI) was 5:4, the CO2 capacity reached 0.112 g of CO2/g of solvent at 40 °C and 1 bar, in which the CO2-rich phase accounts for 95% of the total CO2 capacity and 60% of the total volume. Meanwhile, the energy consumption for CO2 desorption of [N2222][1,2,4-Triz]/N-MI (5:4) was 1.29 GJ/ton CO2, which is 65.78% lower than that of 30 wt % MEA aqueous solution. The results indicated that [N2222][1,2,4-Triz] can react with CO2 to produce carbamate that existed in the CO2-rich phase. Therefore, the original homogeneous liquid was transformed into liquid–solid phase during CO2 absorption due to the great difference in polarity between imidazole organic solvents and carbamate products, as well as strong intermolecular hydrogen bonding between carbamate products. This study provides useful guidance for designing novel phase-change solvents with high CO2 absorption performance and low energy consumption.