Synthesis and catalytic activity of organic–inorganic hybrid Ti-SBA-15 materials

Abstract

Organic-inorganic hybrid Ti-functionalized mesostructured materials have been synthesized from titanocene dichloride in the presence of non-ionic surfactants as structure directing agents in acidic media. The organic functionalization of the mesoporous silica based materials has been accomplished by different techniques, including direct synthesis in the presence of organosilicon precursors, post-synthetic surface silylation and by using bissilylated organosilane precursors to give titanium-containing periodic mesoporous organosilicas (Ti-PMOs). The presence of bissilylated organosilane precursors in the synthesis medium dramatically influences the textural, structural and morphological properties of the synthesized Ti-PMO materials in comparison with Ti-SBA-15 samples. All these materials show high catalytic activity in the epoxidation of 1-octene with hydroperoxides, their catalytic behaviour being correlated with the hydrophobic nature of the sample.

Preparation of superhydrophobic cauliflower-like silica nanospheres with tunable water adhesion

“…Moreover, the silanol content can be derived from 29 Si MAS NMR analysis (see experimental). [43][44][45] Consistent with the results of FT-IR spectra, the silanol content decreases with replacement of Si-OH by more Si-Ph on the surface of these materials. In addition, the compositions of the materials were further characterized by the XPS measurements (Fig.…”

“…2g) suggest that methyl groups were successfully grafted onto the surface via HMDS reacting with silanols. 44 This resulted in the decrease in silanol content. Then it can be speculated that the water-adhesive force should be weakened while the waterrepellent force should be strengthened with the organic modification.…”

“…[43][44][45] In the 29 Si MAS NMR spectra, Q signals, resulting from the hydrolysis and condensation of the TEOS silicon precursor, correspond to silicon atoms directly bonded to other silicon atoms by oxygen bridges. T signals correspond to silicon atoms directly bonded to carbon atoms coming from the incorporation of organosilicon precursors.…”

Cooperative catalysis by silica-supported organic functional groups

“…[16][17][18] A similar hydrophobicity effect has been shown for silylated titanium-containing SBA-15 materials. 19 In these instances, hydrophobic surface groups do not play a direct role in the catalytic mechanism, but rather tune the transport of hydrophobic reactants to the surface and water away from the surface (thus, there is not a true cooperative relationship between the acid and alkyl groups).…”

Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

“…The above-mentioned properties of the inorganic supports will facilitate the applications of the materials in reactions carried at higher temperatures and their use in continuous-flow reactions. In the past decade a lot of research effort has been devoted to the development of adequate procedures to attach homogenous catalysts onto inorganic supports (Merckle & Blümel, 2005;Crosman et al, 2005;Corma et al, 2005;Jones et al, 2005;Melero et al, 2007). Immobilization via covalent bonds is undoubtedly the most convenient, but on the other hand, it is the most challenging method for immobilization to perform on such supports (Jones et al, 2005;Steiner et al, 2004;Pugin et al, 2002;Sandree et al, 2001).…”