Functionalized Ordered Mesoporous Silica by Vinyltriethoxysilane for the Removal of Volatile Organic Compounds through Adsorption/Desorption Process

An organic–inorganic hydrophobic mesoporous silica has been successfully prepared by a co-condensation method with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) as mixed precursors under acidic condition. The synthesized mesoporous silica has been characterized by small-angle X-ray diffraction, transmission electron microscopy, N₂ sorption isotherms, magic-angle spinning nuclear magnetic resonance, and X-ray photoelectron spectroscopy. It is found that the newly synthesized adsorbents exhibit a uniform mesostructure with the vinyl groups embedded into the network of mesoporous silica. Results also show that mesoporous silica could convert from a 2D hexagonal structure (p6m) to a three-dimensional cubic structure (Ia3d) with the increase of the VTES/(VTES+TEOS) molar ratio. This structure transition could significantly increase the surface area, which also proves that VTES exerts a structure-directing effect on co-condensation synthesis. This functionalized mesoporous silica (v-SiO₂) has been applied to test its ability in adsorbing p-xylene. It is observed that these silica materials show improved humidity resistance with the Q_wet/Q_dry increasing from 56.2 to 85.2% (Q_dry and Q_wet stand for the adsorption capacity under dry and wet conditions, respectively). After the adsorption, the adsorbed p-xylene was desorbed from the adsorbents by a vacuum pump. Results show that the desorption ratio of p-xylene could reach up to 88.1% under wet conditions for the adsorbent with the molar ratio VTES/(VTES+TEOS) of 15% (v-SiO₂ (15%)). The adsorption/desorption recycling tests prove that the v-SiO₂ could possess prominent stability with over 96% adsorption capacity being kept after several cycles.