Molecular Manipulation of Two- and Three-Dimensional Silica Nanostructures by Alkoxysilylation of a Layered Silicate Octosilicate and Subsequent Hydrolysis of Alkoxy Groups

Abstract

A novel methodology for constructing molecularly ordered silica nanostructures with two-dimensional (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 [ROSiCl(3), 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.

One-pot synthesis of hierarchical porous layered hybrid materials based on aluminosilicate sheets and organic functional pillars

“…inorganic sheets, as for instance makatite-type, which are forming conventional inorganic layered silicates such as magadiite or kenyaite, 48,49 and silicoaluminates obtained from synthesis gels with high aluminum content. 50 Probably, these types of thin sheets are structured by effective covalent connection between silicon and aluminum tetrahedron, forming intralayer six member rings (6MR) which are along the plane bc of the inorganic layers, such as it was indicated for ECS-type materials. 40 Instracrystalline sodium cations should be located into these intralayer 6MRs, compensating the positive electric charge due to the presence of aluminum framework.…”

Convenient conversion of crystalline layered silicate octosilicate into RWR-type zeolite by acetic acid intercalation

“…Recently, crystalline layered silicates of zeolitic topology have attracted much attention as precursors for the construction of novel zeolites by the topotactic dehydration-condensation of periodic and reactive silanol groups on both sides of the interlayer and high surface area materials by pillaring or delamination. [1][2][3][4][5][6][7][8][9][10][11][12] We have also investigated a new strategy for zeolite synthesis from crystalline layered silicates, and recently succeeded in preparing a thermostable zeolite with the novel framework structure CDS-1 (framework type code: CDO). 1 The CDS-1 zeolite was found to be formed from a novel layered silicate PLS-1 by the topotactic dehydration-condensation between silicate layers, consisting of face-sharing pentagon cylinders.…”

Tailoring surface properties and structure of layered double hydroxides using silanes with different number of functional groups

“…This implies that the number of functional groups in the used silane has a significant effect on the structure and property of the silylated products. More interestingly, Mochizuki et al [12] successfully developed a novel method for constructing molecularly ordered silica nanostructures with two dimensional and three dimensional networks, involving silylation of a layered silicate octosilicate with alkoxytrichlorosilanes and subsequent reaction [20]. Shortly afterwards, Wypych et al successfully synthesized the single-layer LDH silylated products [21].…”