The primary goal of this study is to investigate the potential of particular ionic liquids (ILs) in capturing CO₂ for the sweetening of natural and other gases. The solubility of CO₂ was measured in three distinct ILs, which shared a common anion (Triflate, TfO) but differed in their cations. The selected ionic liquids were {1-Butyl-3-methylimidazolium triflate [BMIM][TfO], 1-Butyl-1-methylpyrrolidinium triflate [BMP][TfO], and 1-Butyl-4-methyl-pyridium triflate [MBPY][TfO]}. The solvents were screened based on results from a molecular computational study that predicted low CO₂ Henry's Law constants. Solubility measurements were conducted at 303.15 K, 323.15 K, and 343.15 K, and pressures up to 1.5 MPa, using a gravimetric microbalance. CO₂ experimental results were modeled using the Peng-Robinson equation of state with three mixing rules. For the three ILs, the Non Random Two Liquid - WS mixing rule regressed the data with the lowest average deviation percentage of 1.24%. The three solvents had similar alkyl chains but slightly different polarities. [MBPY][TfO], with the largest size, exhibited the highest CO₂ solubility at all three temperatures. Calculation of its relative polarity descriptor (N) shows it was the least polar of the three ILs. Conversely, [BMP][TfO] showed the highest Henry's Law constant (lowest solubility) across the studied temperature range. Comparing the results to published data, the study concludes that triflate-based ionic liquids with three fluorine atoms have a lower capacity for CO₂ compared to bis(trifluoromethylsulfonyl)imide (Tf₂N)-based ionic liquids with six fluorine atoms. Additionally, the study provided data on the enthalpy and entropy of absorption. A final comparison shows that the ILs had a lower CO₂ capacity than Selexol, a solvent widely used in commercial carbon capture operations. Compared to other ILs, the results confirm that the type of anion had a more significant impact on solubility than the cation.

In this present work, a task specific ionic liquid (TSIL) was encapsulated into the framework of ZIF-8 to enhance its CO₂ capture capacity and CO₂/N₂ selectivity at post-combustion conditions. 1-Ethyl-3-methylimidazolium amino-acetate [EMIM][Gly] was selected as TSIL. TSIL@ZIF-8 composite sorbents were prepared by varying the loading of TSIL and the sorbents’ thermal stability, porous structure and crystal nature were investigated. Incorporation of TSIL into ZIF-8 has shown dramatic impact on CO₂ uptake especially at below 1.0 bar. At this low-pressure range, CO₂ uptake was higher than the pristine ZIF-8 for all TSIL loadings. TSIL@ZIF-8 composite with 30 wt.% TSIL reached a CO₂ uptake capacity of 0.55 mmol·g^-1 at 0.2 bar which was 6 times higher than the pristine ZIF-8 at the same condition. TSIL incorporated composites also exhibited much higher selectivity than the pristine ZIF-8 at all studied pressures. CO₂/N₂ ideal selectivity at 313 K for 30 wt.% [EMIM][Gly] loading was 28 and 19 at 0.1 and 0.2 bar, respectively. This composite sorbent with significantly higher CO₂ uptake and better CO₂/N₂ selectivity at low pressure region (<1.0 bar) can play an important role in post-combustion CCS processes