A novel, simple, low-cost, energy-efficient, and environment-friendly method for generating pores in a polymer matrix was developed using a combination of an ionic liquid and water pressure treatment. A porous cellulose acetate (CA) matrix was successfully prepared using the ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate (BMIM-BE4) and subsequent water pressure treatment. Pores were generated in the CA polymer matrix when the CA/ionic liquid composite was subjected to water pressure. The characteristics of the thus-generated porous polymer matrix were evaluated using porosimetry and scanning electron microscopy. The pore sizes were ranged from less than 10 nm to over 10 mu M, with an average value of 10 nm. Fourier transform infrared spectra and thermogravimetric analysis showed that when the CA polymer was subjected to water pressure, most of the BMIM-BF4 incorporated in the polymer during its preparation was removed, thereby generating the observed pores. In addition, it was observed that the flux was varied with water pressure, indicating that the pore size was controllable. (C) 2015 Elsevier B.V. All rights reserved.