Absorption and thermodynamic properties of CO₂ by amido-containing anion-functionalized ionic liquids

In this contribution, two kinds of amido-containing anion-functionalized ionic liquids (ILs) were designed and synthesized, where the anions of these ILs were selected from deprotonated succinimide (H-Suc) and o-phthalimide (Ph-Suc). Then, these functionalized ILs were used to capture CO₂. Towards to this end, solubility of CO₂ in the ILs was determined at different temperatures and different CO₂ partial pressures. Based on these data, chemical equilibrium constants of CO₂ with the ILs were derived at different temperatures from the "deactivated IL" model. The other thermodynamic properties such as reaction Gibbs energy, reaction enthalpy, and reaction entropy in the absorption were also calculated from the corresponding equilibrium constant data at different temperatures. It was shown that these anion-functionalized ILs exhibited high CO₂ solubility (up to 0.95 mol CO₂ mol^-1 IL) and low energy desorption, and enthalpy change was the main driving force for CO₂ capture by using such ILs as absorbents. In addition, the interactions of CO₂ with the ILs were also investigated by ¹H NMR, ¹³C NMR, and FT-IR spectroscopy.