Molecular manipulation of two- and three-dimensional silica nanostructures by alkoxysilylation of a layered silicate octosilicate and subsequent hydrolysis of alkoxy groups
Molecular manipulation of two- and three-dimensional silica nanostructures by alkoxysilylation of a layered silicate octosilicate and subsequent hydrolysis of alkoxy groups
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DOI：
10.1021/ja042194e
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发表时间：
2005-05-18
影响因子：
15
通讯作者：
Kuroda, K
中科院分区：
文献类型：
--
作者：
Mochizuki, D;Shimojima, A;Kuroda, K
一种新的方法来构建分子有序的二氧化硅纳米结构与二维（2-D）和三维（3-D）网络已开发通过使用分步过程，涉及硅烷基化的层状硅酸盐/硅酸盐与烷氧基三氯硅烷[ROSiCl 3，R =烷基]和随后的反应在层间空间。烷氧基三氯硅烷几乎完全与硅酸盐反应，桥接硅酸盐层上两个最接近的Si-OH（或-O-）位点，形成新的五元环。未反应的官能团，Si-Cl和Si-OR，很容易水解的后处理与水/二甲基亚砜（DMSO）或水/丙酮的混合物，导致两种类型的硅酸盐结构的形成。用水/DMSO混合物的处理产生了具有偕硅烷醇基团的独特的结晶2-D硅酸盐框架，而水/丙酮混合物诱导相邻层之间的水解和随后的缩合以形成新的3-D硅酸盐框架。2-D结构通过在溶胀的层间空间内存在DMSO分子而保留，并且在DMSO解吸后转化为3-D硅酸盐。结构模型表明，这两种三维硅酸盐都含有新的笼状框架，即使在高温下（丙酮高达380摄氏度），溶剂分子也会被捕获。2-D和3-D二氧化硅结构与已知的层状硅酸盐和沸石类材料完全不同，表明本方法在分子水平上精确设计各种硅酸盐结构的潜力。
A novel methodology for constructing molecularly ordered silica nanostructures with twodimensional (2-D) and three-dimensional (3-D) networks has been developed by using a stepwise process involving silylation of a layered silicate octosilicate with alkoxytrichlorosilanes [ROSiCl3, R = alkyl] and subsequent reaction within the interlayer spaces. Alkoxytrichlorosilanes react almost completely with octosilicate, bridging two closest Si-OH (or -O-) sites on the silicate layers, to form new five-membered rings. The unreacted functional groups, Si-Cl and Si-OR, are readily hydrolyzed by the posttreatment with a water/dimethyl sulfoxide (DMSO) or water/acetone mixture, leading to the formation of two types of silicate structures. The treatment with a water/DMSO mixture produced a unique crystalline 2-D silicate framework with geminal silanol groups, whereas a water/acetone mixture induced hydrolysis and subsequent condensation between adjacent layers to form a new 3-D silicate framework. The 2-D structure is retained by the presence of DMSO molecules within the swelled interlayer spaces and is transformed to a 3-D silicate upon desorption of DMSO. The structural modeling suggests that both of the 3-D silicates contain new cagelike frameworks where solvent molecules are trapped even at high temperature (up to 380 degrees C, in the case of acetone). Both 2-D and 3-D silica structures are quite different from known layered silicates and zeolite-like materials, indicating the potential of the present approach for precise design of various silicate structures at the molecular level.