CuBTC and NH2-CuBTC metal organic frameworks (MOF) were used to produce mixed matrix membranes (MMM) with a block copolymer of poly(ether-b-amide-6) (Pebax (R) MH 1657) as the polymer matrix to investigate the effect of amine functionalized group (-NH2) on the CO2/CH4 gas separation performance of the MMM. The MOF were fully characterized by XRD, FTIR-ATR, TGA, N-2, CO2, and CH4 adsorption, while the MMM were characterized using FTIR-ATR, TGA, DSC, and SEM. Permeability and selectivity of the MMM were studied at different MOF mass contents (5 to 20g/g) and feed pressures (0.3 to 1.5MPa) for pure and mixed gases. The CO2 permeability for 20g/g of both Pebax/CuBTC and Pebax/NH2-CuBTC MMMs was nearly twice that of the neat polymeric membrane, while the presence of amine functionalized group in NH2-CuBTC produced an increasing trend of CO2/CH4 ideal selectivity at high NH2-CuBTC loading and about a 60% increase was observed at 20g/g of NH2-CuBTC.