Abstract：To enhance the CO2 separation performance of mixed matrix membrane （MMM）， the ionic liquid （IL） with good CO2 adsorption properties was first immobilized in mesoporous SiO2， and then the composite material was doped into polyimide polymer to construct a MMM for efficient CO2 separation. The results showed that the immobilized IL mainly entered the inside pores of mesoporous SiO2. When most of the mesoporous pores were filled with ILs， excess ILs would form connectors around the mesoporous SiO2. Due to the excellent adsorption performance of ILs for CO2， the adsorption for CO2 of mesoporous SiO2 was significantly improved after IL immobilization， which further enhanced the CO2 capture by the resulting MMMs incorporating IL@SiO2-doped. With the increase of IL addition in the MMMs， the CO2 permeation performance of the resulting MMMs was also improved. However， when the added amount of IL reached 1.0 g， the IL immobilized mesoporous SiO2 agglomerated in the PI polymer， thus decreasing the CO2 permeability of the resulting MMMs. The permeation performance and ideal selectivity of IL@C-SiO2-2/PI membrane reached the best value， and its ideal selectivity for CO2/N2 could reach 30.