Preparation, characterization and photocatalytic properties of singly and doubly titania-modified mesoporous silicate MCM-41 by varying titanium precursors

A series of titania-modified MCM-41 have been synthesized from varying three kinds of titanium precursors [Ti(OBun)(4), Ti(OBun)(3)(acac), Ti(OBun)(2)(acac)(2)] respectively and mesoporous molecular sieve MCM-41, in which titania existed as single or double layers. The samples were characterized by powder X-ray diffraction (XRD), nitrogen adsorption-desorption at 77 K, Si-29 MAS NMR, FTIR and Raman spectroscopy, as well as by solid state diffuse reflectance UV-VIS spectroscopy. The titanium precursor was cocondensed with the active silanol groups of MCM-41 via Si-O-Ti bonds and the resulting titania modified the mesopore walls of MCM-41 after hydrolysis and calcination. In the titania-modified MCM-41 samples, although the titania species were in an amorphous state and in tetrahedral coordination rather than octahedral coordination, which exists extensively in crystalline titania, they exhibited high photocatalytic activity for the photodecomposition of phenol and the photoreduction of Cr(vi) to Cr(iii).