CO₂ separation performance of polymer membranes can be significantly enhanced by selecting porous fillers with high CO₂ affinity. Ionic liquids incorporation has been recognized as an effective strategy for improving the separation ability of pristine porous fillers. However, the influence of the specific functional groups of ILs in IL@MOF composites on separation performance of MMMs still remains unclear. Herein, we designed three microenvironment-tuned IL@ZIF-8 composites in which the three ILs contain different functional groups (-CH_3, –SO₃H, and –NH₂). Molecular simulation results showed that the NH₂-IL@ZIF-8 has a commendable CO₂ adsorption capacity and CO₂/CH₄ adsorptive selectivity, and the results were well confirmed by the following experimental data. More importantly, the prepared NH₂-IL@ZIF-8 based MMMs also exhibit superior CO₂ separation performance among the three IL@ZIF-8 based MMMs owning to its high CO₂ affinity. Thus, this work can provide guidance for designing IL@MOF composites for MMMs fabrication towards gas separation, and the research mode combining molecular simulation prediction and experimental verification can afford valuable reference for material development in membrane separation field.