High surface area is essential for attachment of functional groups, ions, moieties and nanoparticles. Surface area of fibrous membrane can be enhanced by reducing the fiber diameter or producing the porous fibers. Flow properties of the fibrous membrane can be improved by placing the fibers apart in the fibrous network. By electrospinning, it is feasible to produce the fibrous membrane of specific surface area and Darcy permeability higher than 60 m(2)/g and 1 x 10(-11) m(2), respectively. The interconnected irregular shape mesopores (2-50 nm) within the fibers increase the accessible surface area. On the other hand, presence of macropores (pores larger than 50 nm) largely increases the pore volume (porosity) in fibers and helps to reduce the diffusion resistances. Beaded fibers in the membrane can be used to reduce the bulk transport resistances. We developed a method for incorporating the mesopores and macropores in the nano/microfibers made of engineering plastics. To achieve similar to 60 m(2)/g specific surface area by reducing the fiber diameter, one needs to draw the fibers down to 50-60 nm. In present study, 60 m(2)/g of specific surface area is achieved through the porous fibers of average diameter of 900 nm. A specific surface area result from the porous fiber is much higher than one can achieve by reducing the diameter of fibers. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.