Single crystal mesoporous material

Mesoporous structure was constructed in single crystal particles of niobium and tantalum mixed oxide. TEM and electron diffraction indicated single crystal phase with the mean pore size of 10 nm. The crystallized mesoporous material showed mechanical and hydrothermal stability. 

Mesoporous materials were originally synthesized in irregular bulk or powder forms, which could limit their applications in separation, optics, electronics, and so on. Thus, it is highly desirable to produce mesoporous materials with controllable macroscopic forms. So far, mesoporous materials have been synthesized in a variety of forms including thin films, spheres, fibers, monoliths, rods, single crystals, and nanoparticles. The acidic synthetic route (S+X I+) developed by Huo etal. appears to be the most appropriate for the morphological control of mesostmctures. 

The mesoscaled structural regularity causes various features that are observed for mesoporous materials, such as crystal-like particle morphologies and the existence of sharp XRD peaks. Although no atomic-scaled structural ordering is observed in the mesoporous crystal , these particles can be described as being artificial single-crystalline with a mesoscopic periodic structure. 

The first mesoporous zeolite single crystal (ZSM-5) was synthesized by Jacobsen et al. [20] and since that time a particular attention has been devoted to characterization of this material [ 83, 84 ]. Combination of nitrogen adsorption isotherms, scanning electron... 

The continuous effort of numerous academic and industrial laboratories around the world has resulted in recent years in successful synthesis of a number of new porous materials including new structural types of zeolites and zeolypes, siliceous and non-siliceous mesoporous molecular sieves, mesoporous zeolite single crystals, and micro/mesoporous or micro/macroporous composite materials of different chemical compositions. As a consequence of the success of basic research in this area, zeolites have found new industrial applications. 

The first successful preparation of micro/mesoporous or micro/macroporous molecular sieves as well as mesoporous zeolite single crystals started an intensive search of optimization procedures for their synthesis, to increase their thermal stability and to tailor their acid, base and redox properties for possible applications in heterogeneous catalysis. There is no doubt that mastering of synthesis of these hierarchic materials is an important challenge in the area of porous materials. 

With respect to applications, there will certainly be more and more investigations where ordered mesoporous materials are used as catalysts or catalyst supports. However, the more skeptical note of the section on catalysis shall be repeated here In many cases, much cheaper and simpler alternatives exist, and the properties of ordered mesoporous materials are not so much superior to justify the higher effort of their synthesis. On a longer time scale, non-siliceous compositions will probably be used more frequently in catalysis. If one analyzes the catalytic processes implemented today, the majority is not based on silica as catalyst or support, and the single most important area of aluminumsilicates, acid catalysis by zeolites, seems to be less attractive for ordered mesoporous aluminumsilicates, unless a crystallization of the walls to zeolitic structures or the assembly of such materials from colloidal zeolites to enhance the acid strenght becomes possible. 

P-15 - Synthesis and characterization of the mesoporous material of single crystal particles... 

Mesoporous crystalline M0O3 and WO3 were obtained in thin films. Ordered mesoporous WO3 was first produced using the soft template method. By changing formation conditions, cubic and hexagonal mesoporous structures were obtained. The hard template method using SBA-15 or KIT-6 produced ordered mesoporous crystalline WO3 materials. With SBA-15 as a template, a porous single crystal was formed, while polycrystalline porous WO3 materials were formed with a KrT-6 template,although reaction conditions were similar. 

Organic cations are able to complex silicate anions to form silicate complexes. These complexes can condense to form ultimately microporous zeolite structures. Different templat-ing molecules may form different microcavities. Hence zeolite synthesis is an example of template-directed synthesis. Mesoporous materials can be prepared by using nanometersized micelles preorganized as hquid crystals as a template rather than a single molecule template. 

Coasne B, Grosman A, Dupont-Pavlovsky N, Ortega C, Simon M (2001) Adsorption in an ordered and non-interconnected mesoporous material single crystal porous silicon. Phys Chem Chem Phys 3 1196-1200... 

Characterizing porous media with NMR methods / NMR studies on interfacial phenomena , NMR at single crystal surfaces , Nuclear magnetic resonance and surface phenomena , NMR spectroscopy of self-assembled monolayers , Hybrid mesoporous materials with functionalized monolayers , Nuclear magnetic resonance logging - new effective method for evaluation of reservoir rock properties , Xe NMR of physisorbed xenon. Principles , and Xe NMR of physisorbed xenon. Applications . ... 

---