To gain insight into the influence of metal-organic framework (MOF) fillers and polymers on membrane performance, eight different composites were studied by combining four MOFs and two polymers. MOF materials (NH₂-MIL-53(Al), MIL-69(Al), MIL-96(Al) and ZIF-94) with various chemical functionalities, topologies, and dimensionalities of porosity were employed as fillers, and two typical polymers with different permeability-selectivity properties (6FDA-DAM and Pebax) were selected as matrices. The best-performing MOF-polymer composites were prepared by loading 25wt% of MIL-96(Al) as filler, which improved the permeability and selectivity of 6FDA-DAM to 32 and 10%, while for Pebax they were enhanced to 25 and 18%, respectively. The observed differences in membrane performance in the separation of CO₂ from N₂ are explained on the basis of gas solubility, diffusivity properties, and compatibility between the filler and polymer phases.