The present study explores the fundamental science of estimating sorption of gases in membranes comprised of inorganic porous fillers within a polymer matrix with a novel semi-empirical correlation. The sorption properties of H-2, C3H8, CO2 and CH4 were determined in polydimethylsiloxane (PDMS)/zeolite 4A mixed matrix membranes (MMMs) to assess the viability of these membranes for hydrogen purification and natural gas sweetening. Zeolite filling in MMMs results an increase in solubility over neat PDMS membrane. In addition, incorporation of zeolite 4A to PDMS membrane improved H-2 permeation and H-2/CH4 selectivity. The results confirmed that zeolite 4A can significantly improve the separation properties of poorly H-2-selective PDMS membrane from 0.7 up to 11 and this overcomes the Robeson upper-bound limitation. This improvement was explained referring the Flory-Huggins interaction parameter within MMMs. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.