Structure of hybrid (organic/inorganic) TiO2–SiO2 xerogels as studied by neopentane adsorption at 273 K and Ti K-edge X-ray absorption spectroscopy

TiO2–SiO2 hybrid alcogels prepared from two different `organic siliconʹ precursors, namely Me2Si(OMe)2 and (Me2SiO)3, were characterized by adsorption of neopentane at 273 K and X-ray absorption spectroscopy (XAS) at the Ti K-edge. Simultaneous fitting of the macro- and mesopore (BET), and micropore (Dubinin–Radushkevitch, DR) neopentane adsorption uptakes at 273 K provides a picture of the near-ambient pore structure of these flexible materials. Both X-ray absorption near edge structures (XANES) and EXAFS indicate that micro-segregation into small TiOx particles takes place during acid hydrolysis in the material prepared from the cyclic (Me2Si–O)3 precursor, but a higher Ti dispersion is observed in TiO2–SiO2 hybrid glasses prepared from Me2Si(OMe)2. Spectral features indicative of pentacoordinated Ti dominate the pre-edge XAS structure of the TiO2–SiO2 hybrid glass prepared from Me2Si(OMe)2.