In this work we synthesized Ni2+-containing ionic liquid (IL) 1-methyl-3-[(triethoxysilyl)propyl] imidazolium chloride (TMICl) immobilized on silica to catalyze styrene oxidation with H2O2 for producing benzaldehyde. The catalyst was characterized by Fourier transform infrared (FT-IR) spectroscopy, UV-vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption techniques. The effects of reaction time, reaction temperature, and molar ratio of styrene and H2O2 on the conversion and selectivity were studied at solvent-free condition and in acetonitrile. It was demonstrated that the catalyst was very effective for the reaction. The unique advantage of the catalyst was that the reaction could be carried out at solvent-free condition. This advantage resulted mainly from the fact that both of the reactants, styrene and H2O2, are miscible with the IL, and the Ni2+ was coordinated by the immobilized IL that allowed both reactants to access to active sites of the catalyst effectively. (C) 2009 Elsevier B.V. All rights reserved.