Mixed matrix membranes (MMMs) have shown remarkable progress in the development of high-performance membranes for gas separation. These membranes combine the advantageous properties of both organic polymers and highly selective inorganic fillers. Developments are in process for synthesis and modification of fillers to promote the separation performance. Ionic liquids (ILs) are an emerging class of solvents having high CO2 solubility. In this study, amine based RTIL 3-(trimethoxysilyl) propan-1-aminium acetate APTMSAc was synthesized. Zeolitic imidazolate framework, ZIF-67, was used as inorganic filler due to its shape selective property and appropriate pore size. ZIF-67 was modified by incorporation of RTIL, and subsequently MMMs with Polysulfone (PSf) matrix were prepared. Gas separation data showed that RTIL having �NH2 group as well as acetate ions combined with ZIF-67 nano porous structure and large surface area improved the separation performance of membranes. Increase in selectivity of three component MMMs by 84% and 90% was observed ranging from 39.02 to 72.06 and 39 to 74.47 for CO2/CH4 and CO2/N2 respectively in compared with PSf-RTIL blend membranes. RTIL provided facilitation role in gas permeations due to its high CO2 selective nature. © 2020 Institution of Chemical Engineers