Anatase TiO2 nanosheets with surface acid sites for Friedel-Crafts alkylation

Abstract

The solvothermal synthesis route to mesoporous TiO2 using a vinylphenol polymer structure-directing agent (SDA) was optimized to provide a high yield of bilayer nanosheets. The resultant TiO2 material exhibited a high BET area of 420 m(2) g(-1) after the removal of SDA. Structural analysis of the nanosheets was carried out using powder X-ray diffraction, high resolution-transmission electron microscopy, Raman spectroscopy and solid-state NMR. The results indicated that the TiO2 material consisted mainly of the bilayer nanosheets with (010) facet-dominant anatase crystal structure. The thickness of the nanosheet was 0.75 nm, corresponding to two unit-cell parameters along the b-axis in the anatase crystal system. More than 10% of the surface Ti atoms were terminated with bridging O-H groups and coordinatively unsaturated Ti atoms, which acted as Bronsted and Lewis acid sites. Accordingly, the anatase nanosheets exhibited catalytic performance in the liquid-phase Friedel Crafts alkylation of aromatic compounds.