The aminosilane grafting on micro-sized nanoporous sodium zeolite Y particles was performed and novel mixed matrix membranes (MMMs) were fabricated by embedding the modified particles into the Matrimid (R) 5218 matrix. The aminosilane grafting reaction was considered using 3-aminopropyl (diethoxy)methylsilane (APDEMS) as the silane coupling agent. DLS, BET, XRD, FTIR-ATR, CAM, SEM, and TG/DTG were investigated to characterize the pure zeolite (NaY), silane modified zeolite (Sm-NaY) and the fabricated MMMs. Moreover, the effects of filler content (0-20 wt%) on pure and mixed gas experiments, feed pressure (2-12 bar) and operating temperature (35-75 degrees C) on CO2/CH4 transport properties of Matrimid/Sm-NaY were surveyed. The obtained results revealed that at 15 wt% filler loading (the optimum condition), the CO2 permeability increased from 8.34 Barrer for Matrimid to 9.70 Barrer (about 16%). The related CO2/CH4 selectivity was considerably increased from 36.3 to 571 (about 57%). This superior performance at 15 wt% filler loading was related to the good dispersion of the silane modified NaY particles in the Matrimid matrix. The defect free polymer/filler interface was achieved by the aminosilanes grafted on the external surface of the zeolites. (C) 2015 Elsevier B.V. All rights reserved.