Carbon dioxide permeation studies were conducted on polyether-sulfone (PES) microspheres fabricated using phase-inversion technique by loading various amine-functionalized imidazolium cation ILs with a common anion bis-trifluoromethylsulfonylamide ([TF2N]−) on PES-polymer matrix. The cations include: Aminopropyl-butyl-imidazolium [APBIM], Diethyl-aminoethyl-imidazolium [DEAEBIM], Diaminopropyl-butyl-imidazolium [DMAPBIM]. Breakthrough adsorption of CO2 and CH4 was studied with a feed composition of 20\% CO2, 20\% CH4 and 60\% N2 by weight (4.835 mmol/L of CO2, 13.296 mmol/L of CH4 and 22.794 mmol/L of N2), at flow rates of 22 and 36 mL/min (superficial gas velocities are 0.29 cm/s and 0.47 cm/s). Among the ILs studied, [APBIM] showed maximum CO2 permeation. Results indicate that pore size and porosity are crucial for better CO2 absorption and need of further modification to microspheres morphology. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.