四配位Ti掺杂有机杂化介孔分子筛的直接合成与表征

摘要

以三嵌段共聚物P123为模板剂, NaCl为助剂,1,2-二(三乙氧基甲硅烷基)乙烷为硅源,在水热合成过程中引入钛源,原位一步合成了四配位Ti掺杂在骨架内的SBA-15型有机杂化介孔分子筛( Ti-PMO).利用小角X射线衍射、透射电子显微镜以及低温N2物理吸附等手段表征了Ti-PMO的晶体结构和织构性能,并利用紫外-可见漫反射光谱考察了钛源种类、钛源预水解时间、溶液酸性以及Si/Ti摩尔比对Ti存在形态的影响.研究结果表明,通过精确调控Ti-PMO的合成条件,可使钛源水解产生的低聚中间体与硅源水解产生的低聚中间体充分接触并发生共缩聚,引入的Ti原子能够最终随着水解的氧化硅物种自组装生成有序介孔结构的SBA-15型分子筛,并以四配位形式均匀分布于PMO骨架中.以Cl2 TiCp2为钛源,盐酸浓度为0.18 mol/L时,钛源预水解6 h后加入硅源,在Si/Ti摩尔比大于20时可以得到骨架内四配位Ti掺杂的高度有序介孔结构有机杂化分子筛,其具有良好的热稳定性及水热稳定性.%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 tit-anocene 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 N2 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 tetrahe-dral coordination by finely controlling the synthesis condition. The hydrolysis rate of titanium and silica precur-sors 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-con-densate to form Ti—O—Si structure. Tetrahedral-coordinated Ti-containing PMO with good thermal and hydro-thermal 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.