Intracrystalline structure and physicochemical properties of mixed SiO ₂-TiO₂ sol-pillared aluminosilicate

Highly porous layered inorganic - inorganic nanohybrids were prepared by pillaring SiO₂-TiO₂ nanosol particles with aluminosilicate layers. According to powder X-ray diffraction analysis, the basal spacing of SiO₂-TiO₂ pillared aluminosilicate (STPC) calcined at 400°C was determined to be larger than 40 Å. N₂ adsorption - desorption isotherm measurements showed the STPC to have a large Brunauer - Emmett - Teller surface area of ∼590 m²/g, of which approximately 70% originates from micropores with a size range of 8-16 Å. The sorption behavior of various solvent vapors such as hexane, methanol, and water reveals internal pore surfaces of the STPC to be hydrophobic. A distinct blue shift of absorption edge in UV - vis spectra clearly demonstrates that the nanosized TiO₂ particles are formed between silicate layers as a pillar. Fourier transform infrared and extended X-ray absorption fine structure analysis at the Ti K edge reveals that the pillared titania exists in the form of anatase-structured TiO₂ nanocrystals, not in the form of covalently bonded mixed particles of TiO₂-SiO₂. On the basis of the present findings, we are able to conclude that the quantum-sized TiO₂ and SiO₂ particles are independently intercalated to form a multilayer stacking intracrystalline structure in the gallery space of aluminosilicate clay.