A new way to control the coordination of titanium (IV) in the sol–gel synthesis of broom fibers-like mesoporous alkyl silica–titania catalyst through addition of water

In this research, the tetrahedral and octahedral coordination of Ti(IV) in alkyl silica–titania has been successfully controlled by the addition of water in sol–gel process. Octadecyltrichlorosilane (OTS) and tetraethyl orthotitanate (TEOT) were used as precursors. The effect of the addition of water on the local coordination of Ti(IV) was analyzed by using Fourier transform infrared (FTIR) spectrometer, diffuse reflectance ultra-violet visible (DR UV–Vis) spectrometer, field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) spectrometer and transmission electron microscope (TEM). It was demonstrated that water facilitate the formation of SiOTi bond which is related to the tetrahedral Ti(IV). These materials exhibit the pattern of peak at the small angle of X-ray diffractogram and type IV shape adsorption–desorption isotherms characteristic of mesoporous silica–titania. The mesoporous structure shaped like ‘broom fibers’, arranged by lamellar structure like fibers with diameter size about 3–5 nm has been clearly observed by TEM. The catalytic activity of alkyl silica–titania catalysts obtained was tested in polymerization of styrene in the presence of aqueous hydrogen peroxide. It showed that the presence of the tetrahedral Ti(IV) gave a beneficial effect in increasing the activity in this catalytic reaction.

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► The sol–gel synthesis of mesoporous alkyl silica–titania by addition of water.
► Controlling the tetrahedral and octahedral coordination of Ti(IV) in alkyl silica–titania.
► The formation of mesoporous structure shaped like ‘broom fibers’ alkyl silica–titania.
► The effect of the coordination of Ti(IV) in alkyl silica–titania in polymerization of styrene.