Mesoporous titanosilicates with high loading of titanium synthesized in mild acidic buffer solution

Abstract

Mesoporous titanosilicates with high titanium content were synthesized under mild acidic conditions (pH = 4.4, HAc–NaAc buffer solution) by co-condensation of acetylacetone-modified titanium isopropoxide (Ti(OBu n ) 3 (acac)) and mixture of sodium silicate with tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) or tetrakis(2-hydroxyethyl)orthosilicate (EGMS), using block copolymer Pluronic P123 as template. The combined results of XRD, N 2 sorption and TEM show that the highly regular structure of the mesoporous titanosilicates can still be obtained when Ti/Si molar ratio in the final product is as high as 0.059. The results of UV–vis diffuse reflectance spectra and UV resonance Raman spectra show that the framework titanium species are predominant in the mesoporous titanosilicates when Ti/Si molar ratio in the final product is less than 0.042. The mixture of sodium silicate and EGMS was proved to be the best silicon source for the synthesis of titanosilicates with ordered mesostructure and high titanium content. The efficiency of this synthetic method may be attributed to the mild acidic medium as well as the modified hydrolysis–condensation rate and hydrophility of the precursors.