Efficient CO2/CH4 separation using [Bmim][Ac]/Pebax-1657 supported ionic liquid membranes and its prediction by density functional theory

•Fabrication of composite membranes from Pebax-1657 and 1-Butyl-3 methylimidazolium acetate is done.•Transport properties of fabricated membranes tested with mixed gas composition CO2/CH4.•Both permeability and selectivity were enhanced at a significantly lower concentration of IL.•The ideal selectivity was increased by incorporating IL-modified membranes with 78% more respect to the pristine polymeric membrane. The world's daily increase in population has become ravenous for natural resources for energy and potentially helps to become the main reason for causing global climate change. Carbon dioxide (CO2) is one of the critical elements of the greenhouse gas effect, as we all know. Last few decades, researchers have been much interested in CO2 capture and storage technologies. From such technologies, membrane separation has some good results in CO2 capture compared to others. In this investigation, ionic Liquid (IL) supported membranes were used to separate CO2 and methane (CH4) gas mixtures. The Pebax-1657 with 1-Butyl-3-methylimidazolium acetate concentrations 5%, 10%, 20% (wt.%, based on polymer) were prepared for gas separation study. Density functional theory (DFT) computations were also used to estimate CO2 and CH4 interactions with the IL. These membranes are examined for analytical and morphological research using various characterization methods such as FTIR and scanning electron microscopy. As expected, the gas separation results show that mixed gas selectivity (CO2/CH4) increases at high-pressure values due to the addition of IL. Membrane with 20 wt.% concentration (based on polymer) IL shows higher permeability and CO2/CH4 selectivity. [Display omitted]