A novel composite membrane consisting of a poly(phenylene oxide) (PPO) selective layer and a CMS/Al2O3 substrate was fabricated by a spin-coating method. This new class of PPO/CMS/Al2O3 multilayer composite membranes showed an H-2 permeability of 134 Barrer, two times greater than that for the corresponding self-supported PPO polymeric membrane. High selectivities for H-2/CH4 and H-2/N-2 of 31.8 and 37.1, respectively, were also obtained with this composite membrane. According to field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) observations, using the CMS/Al2O3 material as the substrate provided a smooth surface for the support of the PPO selective layer and increased the roughness from the top to bottom surfaces. The effects of the substrate materials on the permselectivity of the resulting membrane were also investigated. Copyright (c) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.