Ordered mesoporous TiO2 with exposed (001) facets and enhanced activity in photocatalytic selective oxidation of alcohols

Single-crystal TiO2 with 2D and 3D ordered mesoporous structures and exposed (001) facets were synthesized by SBA-15 or KIT-6 templated alcoholysis of TiOSO4 under solvothermal conditions. In the liquid phase photocatalytic selective oxidation of alcohols to aldehydes under UV-light irradiation, the single-crystal TiO2 exhibited much higher activity than the polycrystalline TiO2, since the high crystallization degree favored the transfer of photoelectrons, which might reduce their rate of recombination with holes. Meanwhile, the TiO2 with ordered mesopores showed higher activity than that with disordered mesopores, and the 3D ordered mesoporous channels were more favorable for photocatalytic oxidation than the 2D ordered mesoporous channels, which could be attributed to both the enhanced light harvesting resulting from the multiple light reflections in the pore channels, and the facilitated diffusion and adsorption of the reactant molecules. Also, the exposed (001) facets favored the photocatalytic oxidation due to its high surface energy and increased oxygen vacancies, which reduced the photocharge recombination rate by capturing photoelectrons.