Silica mesoporous templated

In our previous studies, we supported a chiral aminoalcohol, (-)-ephedrine, on Mesoporous Templated Silicas (MTS).8 10 The enantioselective alkylation of benzaldehyde by diethylzinc (Model reaction) was performed using catalytic amounts of the supported aminoalcohol. Our first results8 were in good agreement with precedent results by Soai and al. using silica gel and alumina supported (-)-ephedrine.7 Lower rates, selectivities and enantioselectivities were obtained compared with homogeneous catalysis. 

C. Chamay, S. Begu, C. Tourne-PeteUh, L. Nicole, D.A. Lemer, and J.M. Devoisselle Inclusion of ibuprofen in mesoporous templated silica Drug loading and release property, Eur. J. Biopharm., 57(3) (2004) 533-540... 

Figure 7-13. Examples of membrane characterization results (a) SEM images of a macroporous a-alumina, layer (al), after infiltration of nanophase ceria material (a2) (b) pore size distribution obtained by mercury porosimetry on an a-alumina support (c) typical N2 adsorption-desorption isotherm of a mesoporous templated silica layer and BJH equivalentpore sizes distribution.

Chamay, C., Begu, S., Toume-Peteilh, C., Nicole, L, Lemer, D.A. et al. (2004) Inclusion of ibuprofen in mesoporous templated silica drug loading and release property. European Journal of Pharmaceutics and Biopharmaceutics, 57, 533 0. 

Figure 4.5 TEM image of MCM-41, a surfactant templated silica with ordered mesopores. (Kindly provided by S. Dai, Oak Ridge National Laboratory, Oak Ridge, TN.)...

Figure 15.18 Proposed structures of (a) Pt nanorod wires in silica FSM-16 and (b) Pt nanonecklace wires in organosilica such as HMM-1 (Et-HMM) and HMM-p (Ph-HMM), which are used as the mesoporous templates for nanowire formation.

Hybrid Mesoporous Micelle-templated Silicas (MTS) Containing Organic Base Moieties... 

Brunei, D. Functionalized micelle-templated silicas (MTS) and their use as catalysts for fine chemicals. Microporous Mesoporous Mater., 1999, 27, 329-344. 

Porous carbons were prepared using MCM-48 and SBA-15 mesoporous templates and various carbon precursors (see Chapter 3 for preparation description). Figure 8.11 displays the nitrogen adsorption isotherms at 77 K of SBA-15 and of the corresponding templated carbon obtained by carbonization of sucrose in the template. Both isotherms show a bimodal porosity in the templated carbon, mesopores are generated by the removal of the silica walls, and micropores are present in... 

Some degree of success in supported enantioselective catalysis was accomplished by using functionalisation of mineral support. Due to their unique textural and surface properties, mesoporous micelle-templated silicas are able to bring new interesting properties for the preparation of optically active solids. Many successfully examples have been reported for enantioselective hydrogenation, epoxidation and alkylation. However, the stability of the immobilised catalysts still deserves efforts to allow industrial development of such attractive materials. 

An other approach was followed with a micelle-templated silica of the MCM-41 type. These mesoporous carriers were first grafted with the chlorosilane 7 and then aminated with a guanidine such as TBD 2 11 (Figure 8). 

Figure 37. Nitrogen adsorption-desorption isotherms of parent mesoporous material MTS (solid line), Cl-MTS (dashed line) and tSalpr-MTS (dotted line). MTS = micelle templated silica, Cl-MTS = MTS modified by 3-chloropropylsilane and tSalpr-MTS = MTS modified with Mn(III) iV,iV -bis[3-(3,5-di-ieri-butylsalicylidenamino)propyl]amine.

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. 

The sphere synthesis has been extended into other materials. For example, mesoporous carbon capsules[285] with hollow core and mesoporous shell structures were synthesized using submicrometer-sized solid core and mesoporous-shell silica spheres as templates. 

M.F. Ottaviani, A. Galarneau, D. Desplantier-Giscard, F. Di Renzo, and F. Fajula, EPR Investigations on the Formation of Micelle-templated Silica. Microporous Mesoporous Mater., 2001, 44, 1-8. 

Ottaviani, M.F. et al., EPR investigations on the formation of micelle-templated silica, Microporous Mesoporous Mater., 44, 1, 2001. 

Imperor-Clerc, M., Davidson, R, and Davidson, A., Existence of a microporous corona around the mesopores of silica-based SBA-15 materials templated by triblock copolymers, J. Am. Chem. Soc., 122, 11925, 2000. 

In this respect, the recently discovered family of materials synthetized by silicate condensation around surfactant micelles (Micelle-Templated Silica, MTS) provides unique inorganic support [11,12] due to their regular arrays of uniformly sized channels in the mesopore range of 20-100 A. This solid was recently impregnated with cesium oxides with the aim to obtain superbase catalysts [13]. Nevertheless, the leaching of the basic particles cannot be excluded. In view to avoid such possible phenomena, we have studied the covalent attachment of basic functions such as amino groups on the MTS surface... 

The synthesis and characterization of a chiral amino-alcohol ((1R-2S)-ephedrine) immobilized on MCM-41 type mesoporous silicas (MTS Micelle Template Silicas) are described. The activity of these supported catalysts in the enantioselective addition of diethylzinc to benzaldehyde are reported, and compared with those obtained with the corresponding silica gel supported catalysts. The observed differences are discussed in terms of the nature of the grafting which depends on the support structure. 

The new generation of MCM-41 type mesoporous silicas (MTS Micelle Template Silicas) which are characterized by a regular porosity, consisting of uniformly sized channels with pore diameters within a mesoporous range of 20-100 A [8] have not been used in this type of enantioselective catalysis. Taking into account their characteristic structure, the insertion and grafting of functional molecules is possible as it has been shown recently in this laboratory [9]. 

The pretormed siliceous supports were KiescIgel-60 71 and Micelle Templated Silica (MTS) 72 prepared by published methods and showing textural characteristics similar to those of MC M 4I. namely hexagonal unit cell ao = 4.3 nm surface area 958 in g mesoporous volume 0.76 ml g (33]. 

Van Der Voort P, Ravikovitch PI, De Jong KP et al (2002) Plugged hexagonal templated silica a unique micro- and mesoporous composite material with internal silica nanocapsules. Chem Commun 1010-1011... 

A new family of hybrid organic-inorganic catalysts with dispersed active sites inside ordered mesoporous materials has been prepared by anchorage of transition-metal ligands of Schiff base-type and chiral amino alcohols like (li ,2S)-ephedrine on micelle-templated silicas [180]. Metalation of the grafted ligands with manganese was followed by UV-VIS spectroscopy. 

EISA. The mechanism in each case has been the subject of much research and the current understanding of each mechanism is described below. The other two methods to produce mesoporous templated materials are electrodeposition,which has been successfully used to produce surfactant templated porous metal films from high concentration surfactant solutions, and nanocasting, where a surfactant templated silicate is used as a sacrificial template to generate further porous materials by coating the silica structure in another oxide or carbon precursors. The second material is sintered or solidified, and the silicate removed by HE or high pH solvent wash. This is discussed further in Section 2.10. 

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