Li Defeng, Han Yu, Song Jiangwei, Zhao Lan, Xu Xianzhu, Di Yan, Xiao Feng-Shou
Department of Chemistry & State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130023, China.
Chemistry. 2004 Nov 19;10(23):5911-22. doi: 10.1002/chem.200400188.
Highly ordered hexagonal mesoporous silica materials (JLU-20) with uniform pore sizes have been successfully synthesized at high temperature (150-220 degrees C) by using fluorocarbon-hydrocarbon surfactant mixtures. The fluorocarbon-hydrocarbon surfactant mixtures combine the advantages of both stable fluorocarbon surfactants and ordered hydrocarbon surfactants, giving ordered and stable mixed micelles at high temperature (150-220 degrees C). Mesoporous JLU-20 shows extraordinary stability towards hydrothermal treatment (100 % steam at 800 degrees C for 2 h or boiling water for 80 h), thermal treatment (calcination at 1000 degrees C for 4 h), and toward mechanical treatment (compressed at 740 MPa). Transmission electron microscopy images of JLU-20 show well-ordered hexagonal arrays of mesopores with one-dimensional (1D) channels and further confirm that JLU-20 has a two-dimensional (2D) hexagonal (P6 mm) mesostructure. 29Si HR MAS NMR spectra of as-synthesized JLU-20 shows that JLU-20 is primarily made up of fully condensed Q4 silica units (delta=-112 ppm) with a small contribution from incompletely cross-linked Q3 (delta=-102 ppm) as deduced from the very high Q4/Q3 ratio of 6.5, indicating that the mesoporous walls of JLU-20 are fully condensed. Such unique structural features should be directly attributed to the high-temperature synthesis, which is responsible for the observed high thermal, hydrothermal, and mechanical stability of the mesoporous silica materials with well-ordered hexagonal symmetry. Furthermore, the concept of "high-temperature synthesis" is successfully extended to the preparation of three-dimensional (3D) cubic mesoporous silica materials by the assistance of a fluorocarbon surfactant as a co-template. The obtained material, designated JLU-21, has a well-ordered cubic Im3m mesostructure with fully condensed pore walls and shows unusually high hydrothermal stability, as compared with conventional cubic mesoporous silica materials such as SBA-16.
通过使用碳氟化合物 - 碳氢化合物表面活性剂混合物，在高温（150 - 220摄氏度）下成功合成了具有均匀孔径的高度有序的六方介孔二氧化硅材料（JLU - 20）。碳氟化合物 - 碳氢化合物表面活性剂混合物结合了稳定的碳氟表面活性剂和有序的碳氢表面活性剂的优点，在高温（150 - 220摄氏度）下形成有序且稳定的混合胶束。介孔JLU - 20对水热处理（800摄氏度下100%蒸汽处理2小时或在沸水中处理80小时）、热处理（1000摄氏度下煅烧4小时）以及机械处理（740兆帕压力下压缩）表现出非凡的稳定性。JLU - 20的透射电子显微镜图像显示出具有一维（1D）通道的有序六方介孔阵列，并进一步证实JLU - 20具有二维（2D）六方（P6mm）介观结构。合成态JLU - 20的29Si HR MAS NMR光谱表明，JLU - 20主要由完全缩合的Q4二氧化硅单元（δ = -112 ppm）组成，从不完全交联Q3（δ = -102 ppm）的贡献较小，从非常高的Q4/Q3比率6.5推断，表明JLU - 20的介孔壁是完全缩合的。这种独特的结构特征应直接归因于高温合成，这导致了具有有序六方对称性的介孔二氧化硅材料所观察到的高热稳定性、水热稳定性和机械稳定性。此外，“高温合成”的概念通过使用碳氟表面活性剂作为共模板成功扩展到三维（3D）立方介孔二氧化硅材料的制备。所获得的材料，命名为JLU - 21，具有有序的立方Im3m介观结构，孔壁完全缩合，与传统的立方介孔二氧化硅材料如SBA - 16相比，表现出异常高的水热稳定性。
