Porous aluminum membrane has been prepared by annealing, quenching and acid etching a commercial Al foil. Hydrogen and carbon dioxide permeation and separation properties have been measured under pressure gradient. H-2 and CO2 permeability coefficients for porous Al membrane have been found to increase with increasing etching time, whereas H-2/CO2 selectivity first increases then decreases. In order to improve H-2/CO2 selectivity, composite membrane has been prepared by depositing a thin layer (similar to 8 mu m) of polysulfone (PSF) on the highly porous Al membrane. The optical micrographs show that microstructures of At grain particles and openings of etch pits are of micron order. (C) 2007 International Association for Hydrogen Energy.