Synthesis and Characterization of Titanium-containing Periodic Mesoporous Organosilicas

Titanium-containing periodic mesoporous organosilicas ( Ti-PMO) were hydrothermally synthesized using triblock copolymer P123 as the template, 1,2-bis( trimethoxysilyl) ethane as the silica precursor and titanocene dichloride as the titanium precursor. The crystal and textural properties of Ti-PMO were characterized by X-ray diffraction(XRD), transmission electron microscope(TEM) and N-2 physisorption. The influence of different titanium precursors, prehydrolysis time of titanium precursor, acid concentration and molar ratio of Si/Ti on the form of titanium in PMO were investigated by means of diffuse reflectance UV-Vis spectroscopy. It was revealed that Ti atoms could be incorporated into the framework of PMO materials in the form of tetrahedral coordination by finely controlling the synthesis condition. The hydrolysis rate of titanium and silica precursors should be precisely balanced to bring the oligomer titanium species and oligomer silica species, which are the hydrolysis intermediates of titanium precursor and silica precursor, into intimate contact and then co-condensate to form Ti-O-Si structure. Tetrahedral-coordinated Ti-containing PMO with good thermal and hydrothermal stability can be successfully obtained using titanocene dichloride as the titanium precursor at the ratio of n(Si)/n(Ti) >20 and prehydrolyzed for 6 h at acid concentration of 0.18 mol/L.