The intimidating level of anthropogenic CO2 in the atmosphere responsible for global warming and erratic weather conditions needs to be addressed on a priority basis. Different kinds of materials were used to capture CO2 to curtail the alarming and drastic effects of global warming. An ionic liquid (IL) 1-butyl-3-methylimidazolium methanesulfonate C4mimCH3SO3 was chosen, owing to its unique and efficient characteristics required for CO2 capture. Thermos-physical characteristics such as sigma surface, sigma profile, and sigma potential are calculated from the COSMO-RS model independent of any kind of experimental or coefficient data as an input. The mandatory information required for the interaction of IL with CO2 was obtained from this model. The COSMO-RS model depends upon unimolecular quantum chemical analysis associated with statistical thermodynamics, molecular structure, and conformation. The structural confirmation of C4mimCH3SO3 IL was performed by FTIR, 1H NMR, and 13C NMR spectroscopic methods. Spectrochemical properties are calculated by FTIR, NMR, UV-visible, and fluorescence. Maximum CO2 solubility performed at room temperature (RT) and 45 bar was found to be 2.7 mmol/g. The uptake of CO2 indicates the presence of sulphur-functionalized anions and bulky alkyl groups in IL's significant affinity towards CO2. According to hysteresis-based classification, CO2 sorption and desorption follows type H3 classification, which indicates the presence of microporous and mesoporous in the IL sample. The effect of functionalized anions and alkyl groups on CO2 capture is highlighted in this study. The present study is aimed at providing a detailed overview related to theoretical and experimental study and application in terms of CO2 capture of IL. © 2023 Sami-ullah Rather et al.