Microporous metal-imidazolate framework (MMIF), a highly CO2 selective MOF, was incoporated into a polymeric membrane for separation of CO2 from CH4 and N2 for the first time. MMIF nanoparticles of 50-200 nm were synthesized using the sonication method and dispersed into Matrimid, a commercial polyimide, with MOF loading of 10% and 20% by weight to fabricate mixed matrix membranes (MMMs). Morphology, thermal behavior, and glass transition temperature of the membranes were characterized, and single and mixed gas permeation measurements at 35 °C and 4 bar feed pressure were carried out to reveal their separation performance. Both 10% and 20% MMIF containing Matrimid membranes exhibited enhanced gas permeabilities for all three gases. Contrary to expectations, ideal selectivity of membranes was not improved possibly due to the flexible framework of MMIF. On the other hand, mixed gas permeability measurements showed significant improvement in CO2/CH4 separation factor by 130% and CO2/N2 separation factor by 79% due to competitive adsorption favoring CO2.