A novel facile route, denoted here as IHO∼COO S, was reported to synthesize cubic Im3m mesoporous silicas and metal substituted analogues for the first time by utilizing commercial conventional cationic surfactant cetyltrimethylammonium bromide (CTAB) to direct the mesostructures along with citric acid as the acid media to give a weak acidic condition. This weak acidic system favors not only the fine phase control but also the optimal incorporation of ferric ions, providing a skilful way to prepare the mesoporous composites with a surprising adsorption capability. UV-vis DRS and ESR spectra indicated that the majority of the metal ions inserted into the siliceous framework within the tetrahedral coordination environment. Owing to the controllable incorporation of ferric species that form a monolayer on the channel wall plus the three-dimensional cage-like mesostructure that generates a fine geometric confinement towards the adsorbate, the mesoporous composite overruns zeolite NaY in the instantaneous adsorption of volatile nitrosamines and 1,3-butadiene for the first time. © 2011 The Royal Society of Chemistry.