In this work, we synthesized hypercross-linked porous polystyrene (PS)/ionic liquid (IL) networks by Friedel Crafts alkylation reaction. The obtained porous polymer networks were confirmed by scanning electron microscopy, high resolution-transmission electron microscopy, Fourier-transform infrared spectra and energy-dispersive X-ray spectroscopy. The hypercross-linked porous PS/IL networks showed high surface area (541.13 m(2)/g) and hierarchical porosity compared with non-porous PS membranes (2.52 m(2)/g). The as-prepared hypercross-linked porous PS/IL networks were tested as a catalyst for the reduction of 4-nitrophenol (NP) in aqueous sodium borohydride (NaBH4) solution at ambient temperature. A number of parameters such as catalyst concentration, NaBH4 concentration, and recyclability was investigated for their effect on catalytic performance on the reduction of 4-NP. (C) 2015 Elsevier B.V. All rights reserved.