Intracrystalline Structure and Physicochemical Properties of Mixed SiO2−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 degrees C was determined to be larger than 40 A. N2 adsorption-desorption isotherm measurements showed the STPC to have a large Brunauer-Emmett-Teller surface area of approximately 590 m2/g, of which approximately 70% originates from micropores with a size range of 8-16 A. 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.