Computer‐Assisted Design of Imidazolate‐Based Ionic Liquids for Improving Sulfur Dioxide Capture, Carbon Dioxide Capture, and Sulfur Dioxide/Carbon Dioxide Selectivity

A new strategy involving the computer‐assisted design of substituted imidazolate‐based ionic liquids (ILs) through tuning the absorption enthalpy as well as the basicity of the ILs to improve SO 2 capture, CO 2 capture, and SO 2 /CO 2 selectivity was explored. The best substituted imidazolate‐based ILs as absorbents for different applications were first predicted. During absorption, high SO 2 capacities up to ≈5.3 and 2.4 molSO2 mol IL −1 could be achieved by ILs with the methylimidazolate anions under 1.0 and 0.1 bar (1 bar=0.1 MPa), respectively, through tuning multiple N ⋅⋅⋅ S interactions between SO 2 and the N atoms in the imidazolate anion with different substituents. In addition, CO 2 capture by the imidazolate‐based ILs could also be easily tuned through changing the substituents of the ILs, and 4‐bromoimidazolate IL showed a high CO 2 capacity but a low absorption enthalpy. Furthermore, a high selectivity for SO 2 /CO 2 could be reached by IL with 4,5‐dicyanoimidazolate anion owing to its high SO 2 capacity but low CO 2 capacity. The results put forward in this work are in good agreement with the predictions. Quantum‐chemical calculations and FTIR and NMR spectroscopy analysis methods were used to discuss the SO 2 and CO 2 absorption mechanisms.