Highly Ordered Cubic Mesoporous Materials with the Same Symmetry but Tunable Pore Structures

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• 作者：Pei Yuan ; Jie Yang ; Xiaojun Bao ; Dongyuan Zhao ; Jin Zou ; Chengzhong Yu
• 刊名：Langmuir
• 出版年：2012
• 出版时间：November 27, 2012
• 年：2012
• 卷：28
• 期：47
• 页码：16382-16392
• 全文大小：812K
• 年卷期：v.28,no.47(November 27, 2012)
• ISSN：1520-5827

文摘

In this article, two highly ordered mesoporous silica materials with the same face-centered cubic (fcc) symmetry but distinctly different pore structures have been synthesized by simply changing the amount of silica source. Their structures have been extensively studied by Synchrotron small-angle X-ray scattering, N₂ sorption analysis, scanning and transmission electron microscopy observations, and electron tomography. One mesoporous material formed by a hard sphere packing (HSP) pathway exhibits a bimodal pore distribution, while the other has a conventional FDU-12-type mesostructure with a single-sized pore. By increasing the amount of the silica source, the cavities formed by the packing of composite spherical micelles in the HSP mesostructure are gradually filled by the excess of siliceous species, leading to the conventional FDU-12-type mesostructure with the disappearance of bimodal pores. The pore connectivity of the HSP mesoporous material hydrothermally treated at 150 掳C has been further investigated. Taking advantage of the ultrathin tomographic slices, the sizes of cage, cavity, and connectivity are measured to be 14.5, 10.5, and 6.4 nm, respectively. More importantly, the pore connection between the cage and cavity is directly observed to occur along the 100 direction, different from the FDU-12-type mesostructure in which the connection appears between two adjacent cages along the 110 direction. This work represents an unusual example where two ordered cage-type mesoporous materials with the same symmetry can be synthesized by slightly changing the synthesis condition, but their pore structures and pore connections are significantly different. Our finding is important for understanding the formation mechanism and for the rational design and controllable synthesis of novel mesoporous materials.