Mixed Matrix Membranes (MMMs) have garnered a lot of interest in carbon dioxide (CO2) and methane (CH4) gas separation due to their advantages over pure polymeric membranes. In the present work, various Aluminophosphate-18 (AlPO-18) loadings was incorporated into Polysulfone (PSf) matrix to fabricate MMMs for CO2 gas permeation and separation. The MMMs were subjected to characterization including Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) to study the spectroscopic, crystallographic and morphological characteristics of the developed membranes. CO2 and CH4 gas permeation were conducted to evaluate the effect of different AlPO-18 loading on the gas permeation and separation performance of the membrane. FTIR and XRD analysis proved the incorporation of zeolite AlPO-18 particles on the polymeric matrix. Notable improvements in gas permeation and separation were obtained for MMMs incorporated with 1 wt AlPO-18 (1AlPO-18/PSf MMMs), with the ideal selectivity increasing by 22 in comparison to the pristine PSf membrane. © 2023