Yu Ting, Zhang Hong, Yan Xuewu, Chen Zhengxia, Zou Xiaodong, Oleynikov Peter, Zhao Dongyuan
Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Advanced Materials Laboratory, Fudan University, Shanghai, 200433, P R China.
J Phys Chem B. 2006 Nov 2;110(43):21467-72. doi: 10.1021/jp064534j.
The pore variations of ordered cage-type mesoporous silica FDU-12s have been analyzed in detail by PXRD, SAXS, nitrogen sorption, and electron crystallography. FDU-12s with a cubic symmetry (space group, Fmm) were templated by amphiphilic triblock copolymer F127 with the addition of 1,3,5-trimethylbenzene and KCl under an acidic condition. Three typical samples with different unit cell sizes, pore cage diameters, and entrance sizes were obtained from different synthesis and hydrothermal treatment temperatures, as indicated by the differences in the PXRD and SAXS patterns. The pore structure changes in the three materials were observed by nitrogen adsorption/desorption and 3-D reconstruction of HRTEM images taken from different crystal orientations. The approximate pore structures of FDU-12s can be regarded as a face-centered cubic (fcc) close-packing of spherical cages, each connected to 12 nearest neighboring cages. However, the ideal spherical model is only valid for the FDU-12s prepared at a low temperature (L-FDU-12-100). The cage shape of the FDU-12s synthesized at a high temperature deviates from perfect spheres and is accompanied by an entrance enlargement. The temperature-dependent behavior of the PEO block is discussed with regard to its influence on the micelles and hence the cage configuration. The better understanding of the formation mechanism via the combined characterization techniques and modeling may lead to a more rational approach for tuning the pore cages and entrances of the mesoporous FDU-12 materials.
通过粉末X射线衍射（PXRD）、小角X射线散射（SAXS）、氮吸附和电子晶体学等方法，对有序笼型介孔二氧化硅FDU - 12的孔结构变化进行了详细分析。具有立方对称性（空间群，Fmm）的FDU - 12是以两亲性三嵌段共聚物F127为模板，在酸性条件下加入1,3,5 - 三甲基苯和氯化钾合成的。如PXRD和SAXS图谱所示，通过不同的合成温度和水热处理温度，获得了三种具有不同晶胞尺寸、孔笼直径和入口尺寸的典型样品。通过氮吸附/脱附和从不同晶体取向拍摄的高分辨透射电子显微镜（HRTEM）图像的三维重建，观察了这三种材料的孔结构变化。FDU - 12的近似孔结构可视为球形笼的面心立方（fcc）密堆积，每个笼与12个最近邻的笼相连。然而，理想的球形模型仅适用于低温制备的FDU - 12（L - FDU - 12 - 100）。高温合成的FDU - 12的笼形状偏离完美球体，并伴有入口扩大。讨论了聚环氧乙烷（PEO）嵌段的温度依赖性行为对胶束的影响，进而对笼构型的影响。通过联合表征技术和建模对形成机理有更好的理解，可能会为调控介孔FDU - 12材料的孔笼和入口提供更合理的方法。
