A composite material (FeSIL) prepared by FeCl3-imidazolium ionic liquid grafted on SBA-15 exhibited effective catalytic activity for solvent-free oxidation of styrene into benzaldehyde with high selectivity using H2O2 oxidant and it presented easy recovery and reusability. In situ DRIFTS spectra for styrene and H2O2 adsorption showed that an intermediate Fe3+-pi surface complex on the catalyst surface was responsible for the activation of styrene and its reaction with H2O2 molecules on the surface or in the bulk phase.