PW11/SBA-15介孔杂化材料的直接合成与表征

Direct Syntheses and Characterizations of PW_(11)/SBA-15 Mesoporous Hybrid Materials

采用三嵌段共聚物EO20PO70EO20(P123)为模板剂,正硅酸乙酯(TEOS)和缺位Keggin型多金属氧酸盐Na7PW11O39(PW11)为无机前驱体,由共缩合法一步合成了PW11/SBA-15介孔杂化材料.通过红外(IR)光谱、紫外-可见漫反射光谱(UV-Vis/DRS)、X射线衍射(XRD)、低温N2吸附、透射电子显微镜(TEM)等手段对杂化材料和合成过程进行了表征.结果表明:杂化材料中不仅多金属氧酸盐的Keggin单元保留完整,且共价键联于介孔孔道内部,而且样品基本具有规整有序的六方介孔结构.TEOS预水解时间的长短对有序结构的构筑有明显影响,随预水解时间延长,样品的介观有序性增加.这是因为多金属氧酸盐对模板剂P123有盐析作用,其作用大小与多金属氧酸盐前驱物的溶解度有关.

The hybrid mesoporous materials, PW11/SBA-15, were synthesized using tetraethoxysilane （TEOS） and lacunary polyoxometalate Na7PW11O39 （PWn） by a co-condensation approach in the presence of triblock copolymer EO20PO70EO20 （P123） as a template. The resultant materials were characterized by infrared （IR） spectroscopy, UV-Vis diffuse reflectance spectroscopy （UV-Vis/DRS）, powder X-ray diffraction （XRD）, N2 adsorption-desorption, and transmission electron microscopy （TEM）. Results show that the Keggin units are retained perfectly and grafted onto the pore walls of the mesoporous silica by covalent linkage, and an ordered hexagonal packing of channels with homogeneous pore diameters is obtained in the materials. The prehydrolysis time of TEOS influences the construction of the ordered mesostructure significantly. The long-range ordered mesophase increases as the prehydrolysis time increases because of the salt-out effect of PWn, which is associated with solubility of the polyoxometalate precursors.