The research investigated carbon molecular sieve (CMS) membranes through the dry/wetphase inversion method from the casting polyetherimide (PEI) on alumina support for hydrogen separation. Different coating techniques such as dry method (slide casting followed by drying under vacuum; and spin coating followed by drying under vacuum); and wet method (spin coating and then later kept in an isopropyl alcohol (IPA)/water coagulating bath) at different pyrolysis temperatures of 550, 600 650 degrees C min(-1) were also investigated. The membranes were extensively characterized by field emission scanning electron microscopy (FE-SEM) for surface morphology studies and thermo gravimetric analysis (TGA) for thermal properties. The best performance was obtained from CMS membranes fabricated with the dry-phase method (slide casting/vacuum) and pyrolysis at 600 degrees C, where the H-2/N-2 permselectivity was 16.2. In contrast with the wet-phase, the increase in gas permselectivity by the dry-phase (slide casting/vacuum) was believed to be due to the quick solidification that prevents rearrangement of polymer aggregates and coalescence of the nascent voids formed due to the spinodal or nucleation growth. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.