In. this work, the CO2 absorption working capacity and Solubility in ionic liquids imniobilized into porous solid materials (substrates) Were studied both experimentally and theoretically. The CO, absorption working capacity in the immobilized ionic liquids was measured,experimentally. It was found, that the CO, absorption working capacity and solubility increased up to 10-fold compared to that in the bulk ionic liquids when the film thickness was nearly 2.5 nm in the [HMIm] [NTf2] immobilized in the P25. Meanwhile, a new model was proposed to describe the Gibbs free energy of CO, in the immobilized ionic liquids, and both macro-and microanalyses of the CO2, solubility in the confined ionic liquids were conducted: The theoretical investigations reveal that the substrate has a crucial effect on the gas solubility in the ionic liquid immobilized into the substrates, and the model performance was approved with a consideration of the substrate effect.