C/CMS composite membranes from poly(furfuryl alcohol) for gas separation were successfully prepared, in which porous coal-based carbon tubes with an average pore diameter of 0.11 mu m and a porosity of 40.3% were used as support. The tubular support was coated using viscous poly(furfuryl alcohol) liquid to form an organic layer that was transformed into a thin top layer of carbon membrane after pyrolysis. The gas separation performance of the as-prepared carbon membranes was evaluated at 25, 60 and 80 degrees C by molecular probe method. The morphology and structure changes of C/CMS composite membranes during pyrolysis were examined using SEM, HRTEM, FTIR and XRD techniques. The results show that C/CMS composite membranes with uniform and defect-free thin top layer can be made by one-step coating with viscous poly(furfuryl alcohol) liquid and following pyrolysis. The as-prepared C/CMS composite membranes have excellent gas separation properties for gas pairs such as H-2/N-2, CO2/N-2, O-2/N-2, and CO2/CH, and the highest permselectivity at 25 degrees C can reach up to 465.0, 58.8, 13.2 and 160.5, respectively. It has been found that the permeabilities of the composite membranes decrease while the permselectivities increase as the pyrolysis temperature increases from 300 to 700 degrees C. During pyrolysis, the polymeric structure of poly(furfuryl alcohol) has been transformed into an amorphous turbostratic carbon structure with ultramicropores. For the as-prepared C/CMS composite membranes, the gas separation performance in this work exhibits great competition respect to other carbon membranes reported. These clearly indicate that the C/CMS composite membranes prepared from furfuryl alcohol polymers is a promising membrane for gas separation. (c) 2007 Elsevier B.V. All rights reserved.