Mixed matrix membranes (MMMs) can potentially improve the separation performance of traditional polymeric membranes while still maintaining their processing advantages and lower costs. In this work, MMMs composed of acrylate derivatized polysulfone and functionalized mesoporous MCM-41 were prepared by solution casting. The voids at the polymer-filler interface were removed by the introduction of covalent linkages between the modified polymer and the functionalized fillers. Gas permeation results and SEM images of the synthesized MMMs confirmed a good adhesion and dispersion of the fillers within the polymer matrix. In comparison to MMMs with unmodified MCM-41, covalently linked MCM-41 fillers rendered the MMMs significantly higher CO2/CH4 and CO2/N-2 selectivities due to the presence of a covalent link between the -NH2 group of the filler and the acrylate of the polymer. The highest ideal selectivities obtained here for CO2/N-2 and CO2/CH4 were 32.97 and 31.48 (CO2 permeability=9.13 Barrer), respectively. Different operating temperatures were also studied and activation energies calculated. (C) 2013 Elsevier B.V. All rights reserved.