Large Pore Methylene-Bridged Periodic Mesoporous Organosilicas:  Synthesis, Bifunctionalization and Their Use as Nanotemplates

Abstract

Large pore, methylene-bridged, periodic mesoporous organosilicas (PMO-Me's) have been synthesized using the nonionic surfactant P123 (EO 20 PO 70 EO 20 ) as a structure-directing agent under acidic conditions. The morphology of the PMO-Me materials was observed to be strongly dependent on the acidity of the solution used in each preparation. Modification of the PMO-Me surface with 3-mercaptopropyltrimethoxysilane (MPTS), via a supercritical fluid grafting reaction, resulted in the formation of a bifunctionalized organosilica (SH-PMO-Me). These SH-PMO-Me materials, coated with Au clusters, were subsequently utilized as templates for the supercritical fluid deposition of germanium nanocrystals. The highly hydrophobic surfaces of the SH-PMO-Me templates, and the effective penetrating power of the supercritical fluid, resulted in rapid diffusion of the germanium precursor into the mesopores to produce highly crystalline nanoparticles and nanorods. These nanocomposite materials were found to be significantly more crystalline than those formed from functionalized Au-coated mesoporous silica templates (SH-SBA-15), highlighting the benefits of using PMOs as hosts for the encapsulation of semiconductor nanomaterials.

Synthesis of periodic mesoporous organosilicas functionalized with different amine-organoalkoxysilanes via direct co-condensation

“…The presence of the bridging ethylene moieties in the PMO materials was confirmed by the presence of the CeH vibration bands at 789 and 1415 cm À1 (Fig. 2) [21,36]. The bands corresponding to the SieC bonds in the organosilica precursors were observed at 697 and 1278 cm À1 [14].…”

“…The large weight loss in the second step (200e350 C) was attributed to the thermal decomposition of surfactant molecules. Finally, degradation of the bridging ethylene moieties in the organosilicate framework was observed at around 590 C [21,36]. The weight loss ascribed to the amine-functional groups could not be identified since their decomposition occurred in a similar range to the organic template.…”

Supported Heteropoly Acids and Multicomponent Polyoxometalates as Eco-Friendly Solid Catalysts for Bulk and Fine Chemicals Synthesis

“…Many methods have been reported for the controlled oxidation of 2MN using a series of oxidizing agents in the presence of various catalyst systems [ 61 ]. Stoichiometric oxidation of 2MN using sulfuric acid and chromic acid, about 18 kg of chromium, is produced per kilo gram product (30-60 % yield), causing environmentally hazardous chromium containing waste water [ 62 ]. The use of acetic acid, hydrogen peroxide, and methyl trioxorhenium, as well as, Pd-polystyrene sulfonic acid resin, metalloporphyrin along with potassium monopersulfate and zeolites catalyst systems, has been reported for the oxidation of 2MN [ 63 , 64 ].…”

Organically Modified Micelle Templated Silicas in Green Chemistry

“…Carrying out synthesis of mesoporous catalysts, and reactions using them, in supercritical fluids, is likely to bring significant advantages in terms of the excellent diffusion characteristics of the solvent [8][9][10]. This is particularly likely to be valid where gases are involved (see below).…”