Choosing appropriate filler is a crucial challenge in the preparation of the mixed matrix membranes (MMMs) for the gas separation applications. Hence, the filler type has a significant effect on the filler/polymer interface and gas separation performance relation. In this study, the MMMs were prepared by loading three different nano-fillers including NaX zeolite, ZIF-8 and silica (SiO2) nanoparticles into the poly (ether-block-amide) (PEBA) polymer as a selective layer on the polyethersulfone membrane as a support layer. It was found that porous nanoparticles of NaX and ZIF-8 with the suitable interface and uniform distribution have a much better effect on the microstructure of the MMMs compared to the non-porous SiO2 nanoparticles. Based on the gas permeation results, the incorporation of NaX zeolite and ZIF-8 porous nano-filler up to 2 %wt extraordinarily increased the selectivity of CO2/N-2 from 61.53 to 108.2 and 107.13, respectively, while the loading ZIF-8 (up to 2 %wt) and SiO2 (up to 1 %wt) improved the permeability of CO2 gas to 120% and 44%. In addition, the MMM comprising 2 %wt NaX zeolite had the highest O-2/N-2 selectivity (6.06). (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.