Caged mesostructures

The similar organization energies of the hep and ccp lattices make their intergrowth easy in mesoporous materials synthesized from both simple surfactant and copolymer surfactant. Intergrowth with cubic close-packed (ccp) structure was typically observed 

The SBA-2 crystal growth is plate-like and excellent for making thin films and membranes with the six-fold axis normal to the sheet direction. As expected for this geometry, the unit-cell parameter c a ratio is about 1.62. After calcination, the large 

more extensive TEM studies11351 suggested that the SBA-2 is an intergrowth of hep structure and cep structure. This phenomenon is similar with the case of intergrowth of EMT/FAU in zeolites. The intergrowth phases such as zeolite ZSM-3 and ZSM-20 were believed to be pure hexagonal phase initially. Even so, the index of XRD pattern with Edyinmc symmetry is still the most convenient method to identify SBA-2-type materials. 

The window size of SBA-2 is strongly dependent on the conditions of its synthesis.1-1361 For the low-temperature (—4 °C) synthesis in the presence of high concentrations of the 

Although typical FDU-1 silicas and other polymer-templated silicas with large cagelike mesopores tend to be significantly microporous, the FDU-1 sample calcined at 1000 °C appeared to be essentially free from microporosity, as can be inferred from the relation between its surface area, pore volume, and pore diameter. 

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S.A. El-Safty, T. Hanaoka, and F. Mizukami, Design of Highly Stable, Ordered Cage Mesostructured Monoliths with Controllable Pore Geometric and Sizes. Chem. Mater., 2005, 17, 3137-3145. 

Almost all mesostructures reported far have been governed by the geometrical packing of surfactants. The mesopores are near-cylindrical channels or near-spherical cages. Here is an exception. KSW-2[156] has a mesostructure of rectangular arrangements of square or lozenge-shaped 1-D channels. KSW-2 was synthesized by mild acid treatment (pH value... 

The most successful example is the control of window size of caged mesoporous silica materials synthesized with block copolymer as templates. The pore-entrance diameter of SBA-16 increases as a function of synthesis or hydrothermal-treatment temperature. This is likely to be related to the known phenomenon of the decrease in hydrophilicity of PEO blocks as the temperature increases. In the mesostructure of the F127-silica composite, the cores of the (spherical) micelles are constituted by PPO blocks, whereas the micelle corona, which consists of PEO blocks, interacts with the silica framework. At lower temperature, PEO blocks are expected to favorably interact with hydrophilic silica species and thus to have a tendency to be intimately mixed with the silica framework. When the F127-silica composite is subjected to the treatment at higher temperatures,... 

First preliminary variants of DDM were applied in the full-profile X-ray diffraction structure analysis of a series of new silica mesoporous materials and ordered nanopipe mesostructured carbons. DDM allowed stable back-ground-independent full-profile refinement of the structure parameters of these advanced nanomaterials, a result that was unattainable by any other method. To date, DDM has been applied to many various mesoporous and mesostructured substances. The structural parameters of a series of face-centred cubic (Fm3m), body-centred cubic Im3m), and two-dimensional hexagonal (pGmm) mesoporous silicates were determined by DDM from synchrotron XRD. A comprehensive structural analysis of mesoporous silicates SBA-16 (cage-type cubic Irriim), their carbon replicas, and silica/carbon composites was performed by applying DDM. The structure of MCM-48 mesoporous silicate materials was analysed in detail by DDM from different laboratory and synchrotron XRD data. The pore wall thickness of both as-made and... 

The steps involved in this method are as follows (l)The template materials are highly ordered two-dimensional hexagonal mesoporous silica such as SBA-15 and three-dimensional caged mesoporous silica. (2) Metal precursors are introduced by capillary force, chelation force, and hydrophilic affinity. (3) A thermal treatment is employed to crystallise the guest materials and to form the mesoporous pattern. (4) The template silica is etched by HF or NaOH to obtain self-standing ordered metal oxide guest frameworks with mesostructure. 

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