Study of CO<inf>2</inf> solubility in bicyclic ionic liquids by thermodynamic properties and FT-IR spectroscopic analysis at T=(303.15 and 313.15) K

Ionic liquids (ILs) are alternative substances for post-combustion CO2 captures because of their tunable properties are modified in terms of cation and anion alteration. The basicity and fluorination of either cation or anion of the ILs may increases the CO2 sorption affinity. In this study, four 1,8-diazabicyclo[5.4.0]undec‑7-ene (DBU) based ILs, namely [DBUAc], [DBUTFA], [DBUMSA] and [DBUTFMSA] were used to study the CO2 solubility at various pressures and temperatures. From the pressure-concentration-temperature data, Henry's constant (KH) was predicted to calculate the sorption efficiency of studied ILs. The sign and magnitude of thermodynamic properties such as Henry's constant (KH), Gibbs free energy (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) are reveals that the efficiency of CO2 sorption in ILs. The sorption of CO2 significantly influenced by the temperature and pressure, [DBUAc] showed highest CO2 sorption efficiency (0.7992 mol/mol IL). The experimental and thermodynamic results are confirmed that the solubility efficiency of CO2 as follows: [DBUAc] > [DBUTFAc] > [DBUTFMSA] > [DBUMSA]. Finally, FTIR and COSMO-RS analysis were performed to determine the CO2 sorption efficiency in ILs.