Mesoporous templated synthesis

Template Synthesis and Catalysis of Metal Nanoclusters in Ordered Mesoporous Silicas... 

Zeolites have ordered micropores smaller than 2nm in diameter and are widely used as catalysts and supports in many practical reactions. Some zeolites have solid acidity and show shape-selectivity, which gives crucial effects in the processes of oil refining and petrochemistry. Metal nanoclusters and complexes can be synthesized in zeolites by the ship-in-a-bottle technique (Figure 1) [1,2], and the composite materials have also been applied to catalytic reactions. However, the decline of catalytic activity was often observed due to the diffusion-limitation of substrates or products in the micropores of zeolites. To overcome this drawback, newly developed mesoporous silicas such as FSM-16 [3,4], MCM-41 [5], and SBA-15 [6] have been used as catalyst supports, because they have large pores (2-10 nm) and high surface area (500-1000 m g ) [7,8]. The internal surface of the channels accounts for more than 90% of the surface area of mesoporous silicas. With the help of the new incredible materials, template synthesis of metal nanoclusters inside mesoporous channels is achieved and the nanoclusters give stupendous performances in various applications [9]. In this chapter, nanoclusters include nanoparticles and nanowires, and we focus on the synthesis and catalytic application of noble-metal nanoclusters in mesoporous silicas. 

Fuertes A.B. Template synthesis of mesoporous carbons with a controlled particle size, J. Mater. Chem. 2003 13 3085-8. 

Porous polymer materials, especially in particulate form, are of interest in a diverse range of applications, including controlled drug delivery, enzyme immobilization, molecular separation technology, and as hosts for chemical synthesis [101-104]. MS materials have been used as hosts for the template synthesis of nanoporous polymer replicas through in situ polymerization of monomers in the mesopores [105-108]. 

Most examples discussed so far made use of amorphous inorganic supports or sol-gel processed hybrid polymers. Highly disperse materials have recently become accessible via standard processes and, as a result, materials with various controlled particle size, pore diameter are now available. Micelle-templated synthesis of inorganic materials leads to mesoporous materials such as MCM-41, MCM-48, MSU, and these have been extensively used as solid supports for catalysis [52]. Modifications of the polarity of the material can increase the reactivity of the embedded centre, or can decrease its susceptibility to deactivation. In rare cases, enhanced stereo- or even... 

Template Synthesis of Mesoporous Solids with Supramolecular Assemblies... 

Surface-Mediated Synthesis of Metal/Alloy Nanowires Using Mesoporous Templates... 

Surface-Mediated Synthesis of Metai/AHoy Nanowires Using Mesoporous Templates 603... 

Figure 2.15 General concept of the syntheses of mesoporous materials (a) mesoporous silica synthesis with soft template (b) mesoporous carbon synthesis with hard template.

Combining aspects of carbon and silicon chemistry while at the same time expanding the tool box of the periodic table, recently, a first report on the templated synthesis of mesoporous silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) as analogs of the well-known mesoporous silica materials discussed in many chapters of the book has appeared (Fig. 25.5),58 opening an even wider horizon for the exploration of SiC-related nanomaterials in the fields covered in this book. 

Synthetic aspects template theory for mesoporous oxides synthesis. 7... 

SYNTHETIC ASPECTS TEMPLATE THEORY FOR MESOPOROUS OXIDES SYNTHESIS... 

Keywords photocatalysis, hydrogen evolution, Ti02, semiconductor nanoparticles, sol-gel synthesis, template synthesis, mesoporous materials, metal-semiconductor nanocomposites... 

Complexation of metal ions and subsequent incorporation of the resulting metal complex into the oxide matrix during surfactant-templated synthesis prevents aggregation and leads to a homogeneous distribution of metal centers in the mesostructure. Copper- and vanadium-substituted mesoporous silicas were prepared in this way [107,108], Such materials have great potential in the field of catalysis. 

Figure 1. Schematic representation of the templated synthesis route using mesoporous silicas.

CMK-5 is the first example of the ordered tube-type mesoporous carbons that can be characterized with well-defined Bragg diffractions by ordinary XRD instrument [6]. The XRD pattern of the CMK-5 carbon is distinguished from that of CMK-3 by the much lower intensity of the (100) diffraction. The structure of CMK-5 may be described by the substitution of the carbon nanorods in CMK-3 with nanopipes. The CMK-5 carbon is synthesized using SBA-IS, similar to CMK-3, but the carbon source and synthesis condition are somewhat different from those for CMK-3. The synthesis method for the tube-type carbon can be extended to the SBA-16 mesoporous template. The resultant CMK-7 carbon has a bicontinuous mesoporous structure [15]. 

Fig. 27.5. Mesoporous silica nanoparticles as novel drug delivery systems, (a) Cocondensation method to form functionalized mesoporous silica structures in a surfactant template synthesis, (b) TEM image of mesoporous silica nanoparticles and sketch of a novel drug delivery particle which contains functionalized pores, closed by a gate, and is decorated with ligands for cell targeting, (c) Cell targeting by ligand-receptor interaction at the cell membrane, endosomal uptake and controlled release after pH change from early to late endosome...

The suggested method is based on the concept of the self-ordering of low molecular structure-directed compound in a gelation process. This approach allowed us to purposefully design the pore sizes without additional steps of the template synthesis. Usage of a low-molecular structure forming component does not affect essentially the cost of the final mesoporous material and at the same time provides invariance in modeling of the mesoporous structure architecture. 

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