A strategy for improving CO2 capture by new anion-functionalized ionic liquids (ILs) making use of multiple site cooperative interactions is reported. An extremely high capacity of up to 1.60 mol CO2 per mol IL and excellent reversibility were achieved by introducing a nitrogen-based interacting site on the phenolate and imidazolate anion. Quantum-chemical calculations, spectroscopic investigations, and calorimetric data demonstrated that multiple-site cooperative interactions between two kinds of interacting sites in the anion and CO2 resulted in superior CO2 capacities, which originated from the π-electron delocalization in the pyridine ring.

Five kinds of anion‐functionalized ionic liquids (ILs) with different basicity and substituent were selected, prepared and applied in the capture of SO2 from flue gas, where the concentration of SO2 is only 2000 ppm. The effect of the anion on SO2 absorption capacity, desorption residue, and available absorption capacity under 2000 ppm was investigated. The relationship between available absorption capacity and absorption enthalpy was also studied. Through a combination of thermodynamic analysis and quantum calculation, the results indicated that the effect of the cation in the IL on absorption enthalpy was significant. However, the effect of chain length in the cation was weak. Hence, a new IL with low molecular weight, [P4442][Tetz], was further designed and applied for the capture of SO2, which shows the high absorption capacity of 0.18 g SO2 per g IL and excellent reversibility for 2000 ppm SO2. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2028–2034, 2015

You can have your cake and eat it too: A "dual-tuning" strategy for improving the capture of SO2 was developed by introducing electron-withdrawing sites on the anions to produce several kinds of functionalized ionic liquids. Those functionalized with a halogen group exhibited improved performance over their non-halogenated counterparts, leading to highly efficient and reversible capture.

Ionic liquids are suitable for the absorption of acid gases such as SO 2 because of their unique properties.In this work, a new method was developed for the highly efficient capture of SO 2 by introducing a phenyl group into the azole-based ionic liquids. It was found that these phenyl-containing azole-based ionic liquids reacted with SO 2 through multiple-site interactions between the anion and SO 2 , resulting in an extremely high SO 2 capacity of up to ∼5.7 mole per mole ionic liquid. Spectroscopic investigations and quantum calculations show that the dramatic enhancement in the SO 2 capacity originated from the enhanced π⋯S interaction between the phenyl group on the anion and SO 2 . Furthermore, the captured SO 2 was easy to release by heating or bubbling N 2 through the ionic liquid. This efficient and reversible process using these phenyl-containing azole-based ionic liquids with an enhanced π⋯S interaction provides an excellent alternative to current SO 2 capture technologies. † Electronic supplementary information (ESI) available: NMR and IR data of ionic liquids and SO 2 absorbed ionic liquids, Tables S1, S2, and S3, Fig. S1. See

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