Mesoporous grafting method

Niobium and titanium incorporation in a molecular sieve can be achieved either by hydrothermal synthesis (direct synthesis) or by post-synthesis modification (secondary synthesis). The grafting method has shown promise for developing active oxidation catalyst in a simple and convenient way. Recently, the grafting of metallocene complexes onto mesoporous silica has been reported as alternate route to the synthesis of an active epoxidation catalyst [21]. Further the control of active sites, the specific removal of organic material (template or surfactant) occluded within mesoporous molecular sieves during synthesis can also be important and useful to develop an active epoxidation catalyst. Thermal method is quite often used to eliminate organic species from porous materials. However, several techniques such as supercritical fluid extraction (SFE) and plasma [22], ozone treatment [23], ion exchange [24-26] are also reported. 

This FSMN of high TF was prepared by the simple grafting method using surface reaction between molecules and activated silica surface. It is expected that this simple grafting method could be widely applied to the preparation of other functionalised mesoporous or amorphous silica catalysts. 

The efficiency of new unsymmetrical chiral salen ligands was examined in the asymmetric trimethylsilylcyanation of benzaldehyde. A very high level of enantioselectivity was attainable over chiral Ti(IV) salen complexes prepared from salicylaldehyde and 3,5-Di-/ert-butylsalicylaldehyde derivative as compared to the conventional salen catalyst. Enantiomeric excess of the corresponding reaction product was generally more than 70% over unsymmetric chiral salen catalysts. The chiral Titanium(IV) salen complexes immobilized on a mesoporous MCM-41 by multi grafting method showed a relatively high enantioselectivity for the addition of trimethylsilyl cyanide to the benzaldehyde. 

To improve the hydrophobicity of Ti-containing mesoporous silicas, cocondensation and grafting method with the organosilanes can be used... 

FIGURE 4.1 Schematic representation of functionalization of mesoporous silicas by the postsynthesis grafting method. 

The chiral vanadyl salen complex was anchored on mesoporous materials by a covalent grafting method. These heterogenized complex catalysts were evaluated as asymmetric catalysts for the asymmetric oxidation of sulfides to sulfoxides [92]. 

Abstract A review of the thermolytic molecular precursor (TMP) method for the generation of multi-component oxide materials is presented. Various adaptations of the TMP method that allow for the preparation of a wide range of materials are described. Further, the generation of isolated catalytic centers (via grafting techniques) and mesoporous materials (via use of organic templates) is simimarized. The implications for syntheses of new catalysts, catalyst supports, nanoparticles, mesoporous oxides, and other novel materials are discussed. 

The results for cyclooctene epoxidation with TBHP show that the method of heterogenisation plays a decisive role in the activity (Table 6). Indeed, the materials obtained from the complex grafted onto a fimctionahsed matrix (odd entries. Table 6) are less active (seen by comparing TOP values) than those synthesised via the tethering of fimctionahsed complexes on a mesoporous material (even entries. Table 6). 

Epoxidation over niobium or titanium grafted mesoporous molecular sieves where template was removed by solvent exchange method prior to calcination ... 

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