Direct synthesis of highly ordered Co-SBA-15 mesoporous materials by the pH-adjusting approach
Direct synthesis of highly ordered Co-SBA-15 mesoporous materials by the pH-adjusting approach
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DOI：
10.1016/j.micromeso.2007.06.020
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发表时间：
2008-04
影响因子：
5.2
通讯作者：
Z.-W. Lou;Ruiheng Wang;Hui Sun;Yuan Chen;Yanhui Yang
中科院分区：
文献类型：
--
作者：
Z.-W. Lou;Ruiheng Wang;Hui Sun;Yuan Chen;Yanhui Yang
采用氢氧化钠“调pH”法，在温和条件下（pH>2.0）直接合成了钴取代SBA-15（Co-SBA-15）介孔材料。粉末X射线衍射（XRD）、N2物理吸附和高分辨透射电子显微镜（HRTEM）等表征结果表明，合成的材料具有高度有序的六方介孔结构，且与合成溶液的pH值密切相关。在pH为3.0时得到的Co-SBA-15样品具有最佳的结构。固态魔角旋转核磁共振（MAS NMR）的结果表明，在较高的pH值下的缩合较少。此外，pH值也强烈影响钴阳离子在二氧化硅框架中的掺入。Co-SBA-15样品的紫外-可见漫反射吸收光谱和氢气程序升温还原（H2-TPR）结果表明，钴离子在SiO2骨架中处于四面体配位。研究了pH值和Na（NaOH）的加入对Co-SBA-15介孔结构和Co离子嵌入量的影响。
Cobalt-substituted SBA-15 (Co-SBA-15) mesoporous materials were directly synthesized under mild conditions (pH>2.0) by a “pH-adjusting” method using sodium hydroxide. Characterization results, such as powder X-ray diffraction (XRD), N2physisorption and high-resolution transmission electron microscopy (HRTEM), showed that the resultant materials exhibit highly ordered hexagonal mesoporous structures, which was strongly correlated to the pH in the synthesis solution. The Co-SBA-15 sample obtained at pH of 3.0 gave the best structure. Solid state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated less condensation under higher pH. In addition, the pH also strongly affected the incorporation of cobalt cations in the silica framework. Diffuse reflectance UV–vis absorption spectra of calcined Co-SBA-15 samples and hydrogen temperature programmed reduction (H2-TPR) demonstrated that the cobalt ions in the silica framework locate at tetrahedrally coordinated sites. The effect of pH and sodium (NaOH) addition on improving the cobalt ion incorporation and the mesostructure of Co-SBA-15 materials were also discussed.