MICROPOROUS and mesoporous inorganic solids (with pore diameters of ≤20 A and ∼20–500 A respectively)1 have found great utility as catalysts and sorption media because of their large internal surface area. Typical microporous materials are the crystalline framework solids, such as zeolites2, but the largest pore dimensions found so far are ∼10–12 A for some metallophosphates3–5 and ∼14 A for the mineral cacoxenite6. Examples of mesoporous solids include silicas7 and modified layered materials8–11, but these are invariably amorphous or paracrystalline, with pores that are irregularly spaced and broadly distributed in size8,12. Pore size can be controlled by intercalation of layered silicates with a surfactant species9,13, but the final product retains, in part, the layered nature of the precursor material. Here we report the synthesis of mesoporous solids from the calcination of aluminosilicate gels in the presence of surfactants. The material14,15 possesses regular arrays of uniform channels, the dimensions of which can be tailored (in the range 16 A to 100 A or more) through the choice of surfactant, auxiliary chemicals and reaction conditions. We propose that the formation of these materials takes place by means of a liquid-crystal 'templating' mechanism, in which the silicate material forms inorganic walls between ordered surfactant micelles.

Ordered mesoporous molecular sieves synthesized by a liquid-crystal template mechanism

The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.

http://dns2.asia.edu.tw/~ysho/ysho-english/1000 wc/pdf/j ame che soc114, 10834.pdf

A new family of mesoporous molecular sieves prepared with liquid crystal templates

"Space—the final frontier." This preamble to a well-known television series captures the challenge encountered not only in space travel adventures, but also in the field of porous materials, which aims to control the size, shape and uniformity of the porous space and the atoms and molecules that define it. The past decade has seen significant advances in the ability to fabricate new porous solids with ordered structures from a wide range of different materials. This has resulted in materials with unusual properties and broadened their application range beyond the traditional use as catalysts and adsorbents. In fact, porous materials now seem set to contribute to developments in areas ranging from microelectronics to medical diagnosis.

Ordered porous materials for emerging applications

A critical review of adsorption methods that are currently used in the characterization of ordered organic−inorganic nanocomposite materials is presented, and the adsorption methodology that is potentially useful for this characterization, but has not yet been applied, is discussed. The ordered organic−inorganic nanocomposites include surface-functionalized ordered mesoporous materials (OMMs) with siliceous frameworks (synthesized either via postsynthesis surface modification or via direct co-condensation method), periodic mesoporous organosilicas, and surfactant-containing OMMs. This review covers the methods for determination of the specific surface area and pore volume. The available methods for mesopore size analysis are critically compared and evaluated, with special emphasis on the recent developments related to the application of advanced computational methods for studying adsorption in porous media and to the direct modeling of adsorption using highly ordered surface-functionalized OMMs as model a...

Gas adsorption characterization of ordered organic-inorganic nanocomposite materials

Mesoporous organic-inorganic hybrid materials, a new class of materials characterized by large specific surface areas and pore sizes between 2 and 15 nm, have been obtained through the coupling of inorganic and organic components by template synthesis. The incorporation of functionalities can be achieved in three ways: by subsequent attachment of organic components onto a pure silica matrix (grafting), by simultaneous reaction of condensable inorganic silica species and silylated organic compounds (co-condensation, one-pot synthesis), and by the use of bissilylated organic precursors that lead to periodic mesoporous organosilicas (PMOs). This Review gives an overview of the preparation, properties, and potential applications of these materials in the areas of catalysis, sorption, chromatography, and the construction of systems for controlled release of active compounds, as well as molecular switches, with the main focus being on PMOs.

Silica-based mesoporous organic-inorganic hybrid materials.

Single layered polysilicate kanemite (NaHSi2O5·3H2O) was allowed to react with alkyltrimethylammonium chloride solutions to form alkyltrimethylammonium–kanemite complexes. During the organic intercalation, the SiO2 layers in the complexes were condensed to form three-dimensional SiO2 networks. The calcined products of the complexes had micro pores 2–4 nm in diameter, and the surface areas were ca. 900 m2g−1. The pore size of the calcined products was altered with the variation in the alkyl-chain length of the alkyltrimethylammonium ions employed.

The preparation of alkyltrimethylammonium-kanemite complexes and their conversion to microporous materials.

Syntheses of Intercalation Compounds of Layered Niobates with Methylviologen and Their Photochemical Behavior

Intercalation of 2, 2′-Bipyridine and Complex Formation in the Interlayer Space of Montmorillonite by Solid-Solid Reactions

Montmorillonite-organic intercalation compounds were prepared by solid-solid reactions using acrylamide, methacrylamide, and urea as the guest organic molecules. It took only a few minutes to complete the reaction even when dried montmorillonite was used.

Preparation of Montmorillonite-Organic Intercalation Compounds by Solid-Solid Reactions

To develop a new type of carbothermal reduction for the preparation of nitrides, a montmorillonite-polyacrylonitrile intercalation compound was heated inflowing N2 using intercalated polyacrylonitrile as a reducing agent. Nitridation occurred at >1150°C, and β-sialon was obtained, with the formation of β-Sic and AlN.

Synthesis of β-sialon from a montmorillonite-polyacrylonitrile intercalation compound by carbothermal reduction

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