Confined growth of TiO2 nanoclusters inside mesopores of core–shell silica spheres with high loading as efficient photocatalysts

In a mixed solvent composed of acetonitrile and ethanol, tetrabutyl orthotitanate (TBOT) was quickly introduced into the pores of the core–shell silica particles (SiO 2 @ d SiO 2 ) using the coordination bond formed between N and Ti. Since all the hydrolysis reactions of TBOT occurred in the pores, SiO 2 @ d SiO 2 spheres coated with TiO 2 (S@S@TiO 2 ) with an effective loading of TiO 2 as high as 74% were obtained. Because all TiO 2 nanoclusters are located in the pores, their growth is restricted by the pores. So the size of crystalline grains in the pores of the shell slowly increases with the increase in the calcination temperature. Due to the confined growth of TiO 2 nanoclusters, S@S@TiO 2 still maintains the anatase phase when the calcination temperature is as high as 1050 °C, which is significantly higher than the maximum thermal stability temperature of 900 °C reported in the literature. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the catalytic activity of S@S@TiO 2 calcined at 950 °C is 2.1 times higher than that of the commercial P25 TiO 2 photocatalyst. Graphical abstract