Transparent self-standing films of titanium-containing nanoporous silica

Transparent self-standing films of titanium-containing (Ti/Si ratio of 1/50) silica-surfactant mesostructured materials, having a thickness of ca. 50 μm and a lateral size of a few centimeters, were synthesized by the solvent evaporation method from tetramethoxysilane, vinyltrimethoxysilane, titanium tetraisopropoxide, and octadecyltrimethylammonium chloride. The films were converted to titanium-containing nanoporous silica films by subsequent calcination in air at 550 °C, while their highly ordered mesostructures and macroscopic morphology were retained after the surfactant removal. Titanium-containing nanoporous silica films with hexagonal and cubic symmetry were obtained by changing the composition of the starting mixtures. The resulting materials possess a large surface area (ca. 900 m²/g) as evidenced by nitrogen adsorption/desorption isotherms. The titanium ions exist in the silica network as a tetrahedrally coordinated species. UV irradiation of the titanium-containing nanoporous silica film in the presence of CO₂ and H₂O led to the evolution of CH₄ and CH₃OH, indicating the photocatalytic reactivity of the present material.