| The integration of organic and inorganic fragments within the pore wall of the periodic mesoporous organosilica (PMO) represents one of the recent breakthroughs in the fields of material science. The thermal, hydrothermal and mechanical stability of PMO materials are increased due to the presence of organic bridging groups distributed uniformly in the mesoporous framework. Therefore, metal containing PMOs exhibit better structural properties and catalytic performance in some organic reactions than their silica counterparts.PMO materials with highly ordered mesoporosity have been successfully synthesized using hydrothermal method. The influence of molar ratio of Si/P123, acid concentration, crystallization time and addition of NaCl on the crystallinity and textural properties of PMO was investigated. The optimized preparation conditions were:Si/P 123=50-75, acid concentration of 0.18 mol/L HC1, crystallization time of 48h and NaCl/Si=4.Titanium containing periodic mesoporous organosilicas (Ti-PMO) have been hydrothermally synthesized and 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 was investigated. 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 and then Ti will be successfully incorporated into the framework of PMO, as isolated tetrahedral sites.Ti-PMO has better thermal, hydrothermal and mechanical stability than Ti-SBA-15 and exhibits a better catalytic performance in the epoxidation of allyl chloride. |
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