Through a spin-coating technique, a high performance carbon molecular sieve (CMS) membranes were fabricated from thermally stable polymer polyphenylene oxide (PPO) and thermally labile polymer poly vinylpyrrolidone (PVP). The permeation results show that the small gas molecules (H-2, CO2, N-2, and CH4) transport mechanism is dominated by the molecular sieving effect. The permeation performances have a strong dependency upon polymer concentration and pyrolysis temperature. The best performance for hydrogen permeability obtained with PPO 15 PVP pyrolyzed at 700 degrees C was 1121 Barrer (1 Barrer = 1 x 10(-10) cm(3) (STP)cm/[cm(2) s cm Hg]) and the values of selectivity for gas pairs such as H-2/N-2 and H-2/CH4 were 163.9 and 160.9, respectively. The correlation factor of permselectivity of H-2/N-2 and H-2/CH4 gas pairs obtained from PPO and PPO/PVP derived CMS membranes were above the Robeson (2008) upper bound. The addition of thermally labile PVP creates diffusion pathways and controls selectivities for the CMS membranes derived from PPO 10 PVP and PPO 15 PVP. (C) 2011 Elsevier B.V. All rights reserved.