Depending on the synthetic conditions (surfactant, acid, base, and presence or absence of TEOS), the sol–gel polymerization of functionalized polyorganosiloxane affords various textured silica-based materials.

Polysaccharides are a new class of pervasive biopolymers that display many advantages including wide availability, sustainability, inherent inclusion of chemical functionality, biocompatibility and biodegradability. Current efforts are focused on the catalytic transformation of these macromolecules into fuels and platform chemicals. However, there is growing interest in using biopolymers directly to create functional materials. Particularly, the ability of some polysaccharides to form physical and chemical porous hydrogels has opened new avenues for material synthesis and has been the driving force for rethinking the strategies used to create value-added nanomaterials from naturally available biomass. Among them, chitosan is on the rise due to the presence of amino groups on the polymer backbone that distinguishes it as a unique natural cationic polymer. This contribution sheds light on the opportunities offered by engineering the secondary structure of chitosan fibrillar hydrogels. The optimization and stabilization of the open framework structure of these soft-materials are crucial to designing novel functional hybrid materials, dispersed chitosan-metal nanoparticles and hierarchical porous inorganic materials.

Polysaccharides are a new class of pervasive biopolymers that display many advantages including wide availability, sustainability, inherent inclusion of chemical functionality, biocompatibility and biodegradability. Current efforts are focused on the catalytic transformation of these macromolecules into fuels and platform chemicals. However, there is growing interest in using biopolymers directly to create functional materials. Particularly, the ability of some polysaccharides to form physical and chemical porous hydrogels has opened new avenues for material synthesis and has been the driving force for rethinking the strategies used to create value-added nanomaterials from naturally available biomass. Among them, chitosan is on the rise due to the presence of amino groups on the polymer backbone that distinguishes it as a unique natural cationic polymer. This contribution sheds light on the opportunities offered by engineering the secondary structure of chitosan fibrillar hydrogels. The optimization and stabilization of the open framework structure of these soft-materials are crucial to designing novel functional hybrid materials, dispersed chitosan-metal nanoparticles and hierarchical porous inorganic materials.

The synthesis of highly active acid catalysts supported on ordered mesoporous materials has eluded chemists until 1998, when Wim M. Van Rhijn et al. explored three different routes to tether sulfonic acid on mesoporous silica. This viewpoint sheds light on this landmark and explores its significant impact on material science and green catalysis.

Organic-inorganic hybrid materials with different levels of structuration and porous hierarchy and one or several types of active sites in the framework can catalyze multistep chemical processes in a one-pot reactor system following a cascade of reaction events. It will show how the different active sites can act in a synergistic or in a consecutive way following a similar functionality model to biological multisite catalysts. Research on this subject for heterogeneous catalysts is still in the beginning stage and very interesting results can be expected if we are able to successfully combine the properties of organic and inorganic catalysts.

The self-assembly and sol-gel polymerisation of novel alkoxysilane-functionalized polymethylsiloxanes provide versatile access to nano-assembled containers, silica-based micro- and nano-architectures and dispersed mixed metal oxide hybrid materials.

This manuscript describes the synthesis and structural study of new second generation Hoveyda-Grubbs catalysts: 1,3-dimesityl-acenaphthylenyl-4,5-imidazolin-2-ylidene (BIAN-NHC) ruthenium isopropoxybenzylidene dichloride and 1,3-bis(2,6-dimethylphenyl)-2,3-dihydro-1H-imidazole Cl(2)Ru(=CH-o-O-i-PrC(6)H(4)) . The electrochemical and catalytic behavior of these new complexes was compared with the conventional NHC carbene Hoveyda II IMes-type complexes and for ring closing metathesis reactions.

The co-condensation of functional alkoxysilanes with tetraethoxysilane in the presence of a structure directing agent under sol-gel process chemistry is a common way to access functional organosilica with an ordered mesostructure. In this report, bulky silylated fatty acid methyl esters were used both as co-templating bio-molecules and functionalizing agents in the process of supra-molecular silica mineralization. The highest structural regularity in terms of pore size distribution and channel size homogeneity was observed for carboxy-tethered silica possessing SBA-15-type architecture due to an enhanced fatty acid precursor-surfactant interaction. The carboxylic surface embedded within the hydrophobic environment of the fatty compounds confers to these materials interesting reactive-surface properties with promising applications as drug-delivery systems and bio-catalytic nanoreactors.

The ability of chitosan biopolymer to coordinate vanadium, tungsten and molybdenum metallic species and to control their mineralisation growth provides a new family of surface-reactive organic-inorganic hybrid microspheres. Drying the resulting materials under supercritical conditions allowed the gel network dispersion to be retained, thereby leading to a macroporous catalyst with surface areas ranging from 253 to 278 m(2) g(-1). On account of the open framework structure of these microspheres, the redox species entangled within the fibrillar network of the polysaccharide aerogels were found to be active, selective and reusable catalysts for cinamylalcohol oxidations.

Organosilica materials with different contents of Troger's base (TB) as builder moieties have been synthesized from previously synthesized bis-trialkoxysilylated Troger's base. Three well-nanostructured hybrid mesoporous materials were prepared through different approachs: (a). anchoring the TB on a preformed silica SBA-15 material by postsynthesis grafting, (b) incorporating the TB fragments into the rigid and ordered periodic mesoporous organosilica (PMO) with hexagonal structure (HMS) by self-assembling process, and (c) using anion fluoride as catalyst for a sol-gel synthesis process in the absence of structural directing agents (SDAs), at neutral pH and low synthesis temperature, to introduce the TB units into the walls of high surface orderless mesoporous materials with flexible structure. The degree of long-range ordering of the materials was determined from X-ray diffraction and transmission electron microscopy and the texture of the various samples were analyzed by nitrogen sorption volumetry. The composition of the materials was determined by elemental analyses and thermogravimetry, and the integrity, topology and structuration level of the Troges base units were characterized by C-13 NMR and Si-29 MAS NMR spectroscopy. The materials were used as basic organocatalysts in Knoevenagel reaction. The disordered mesoporous hybrid materials, show the highest catalytic activity due to the appropriate combination of high accessibility and structural flexibility. These mesoporous organosilica materials are stable upon recycling.

The porous organosilica framework containing Troger's base (TB) prepared by mild sol-gel synthesis from 2,8-bis-silylated TB precursor contains a mixture of two point attached TB and one point attached TB units, resulting from unexpected partial Si-C bond cleavage as demonstrated by Si-29 MAS NMR spectroscopy and by selective chemo-desorption of the anchored organic part of the hybrid material.

This work describes the synthesis of novel functional silica materials with difunctional thiol-amide substructures and featuring regular architectures on a mesoscopic level. The functional materials were synthesised by both one-pot co-condensation and post-grafting approaches. The thiol groups confined in the matrix were found to be efficient for palladium entrapment, leading to highly active and reusable heterogeneous catalysts for Sonogashira and Suzuki-Miyaura cross-coupling reactions. This work evidences the crucial role of both the thiol precursor and the condensation degree of the silica scaffold in view of the design of stable and reusable tailor-made mesoporous catalytic silica materials.

In the present work we report a "green" method for the grafting of organic monolayers at the surface of silica nanoparticles using water as a solvent. This method is based on the use of water-stable phosphonic acid coupling molecules grafted on an intermediate layer of aluminium species, as the sensitivity of Si-O-P bonds toward hydrolysis precludes a direct anchoring onto silica. Two approaches were explored: anchoring of octylphosphonic acid on aluminated silica and one-pot modification of silica by AlCl3 then by octylphosphonic acid. The modified powders were characterized using elemental analysis, P-31 and Al-27 MAS NMR spectroscopy, FTIR spectroscopy and N-2 physisorption. The one-pot approach appears particularly promising, as it allows the anchoring on silica of phosphonic acid monolayers with controlled densities in a significantly shorter time.

The reaction of octylphosphonic acid with the surface of alumina nanoparticles has been investigated in order to prepare a close packing of grafted-alkyl chains. This goal was attained through a fitting selection of the experimental conditions in terms of pH, reactant amount, reaction time and temperature. DRX, TEM and P-31 MAS NMR spectroscopy are all consistent with an efficient covalent anchorage of the alkylphosphonate chains without degradation of the support, demonstrated by the morphology and texture preservation during the modi. cation. In addition to the textural analysis, nitrogen adsorption isotherms provide additional pieces of information on the interaction energy between the nitrogen molecule and the surface. These data, combined with those supplied by the empirical test of floatability of powders (methanol number test), as well as the adsorption properties of the differently functionalized alumina samples using other probes, such as hexane and water, as a function of the chain loading, provided converging information about surface coverage and the hydrophilic/hydrophobic properties of the various materials. Different conformations are proposed to take into account the different results obtained from vapor adsorption measurements.

Hydrophilic chemically stable porous silicon surfaces are generated by surface functionalisation with polar head terminated lipid biomolecules of the monoglyceride type. Two approaches to anchor the monoglyceride moiety to porous silicon surfaces are presented.

One of the fundamental enzymatic catalyst assets, which is the most difficult to engineer in synthetic systems, is the coexistence of multifunctional sites and their synergetic cooperation. In this work, an efficient approach toward cooperative acid-base materials using natural matrices is proposed. Taking advantages from chitosan polysaccharide as nano-assembling system and on the supercritical drying technique to preserve their porosity, the mutual interactions between different glucosamine units and the Lewis acidic precursors (Ti, Zr, Al, Sn) allowed the preparation of hierarchically porous microspheres in which well-separated amino groups from chitosan are replicated with highly dispersed acidic inorganic oxides. This decoration at the nano-scale entails a notable improvement on the hydrothermal stability of the resulting organic-inorganic hybrid materials. The resulting acid-base hybrid materials are assessed for three carbon-carbon forming reactions (Henry condensation, Michael addition and jasmin-aldehyde synthesis) and systematically compared to the pure acidic inorganic oxide and basic chitosan microspheres. The bifunctional materials displayed interesting catalytic activity and selectivity, with respect to monofunctional ones, witnessing thus on the cooperative effect attainable in chitosan@inorganic oxide microspheres. (C) 2010 Elsevier Inc. All rights reserved.

This work describes a versatile strategy for fabricating highly porous and nanofibrous titania, zirconia, alumina and tin oxide. Taking advantage from chitosan polysaccharide microspheres as nano-assembling system during sol–gel mineralization of monomeric alkoxides and the beneficial effect of supercritical CO2 drying to avoid the collapse of the transient hybrid material network, all targeted metal oxides were created, after calcinations, as fibrous filaments featuring dual meso- and macro-porous network with surface areas ranging from 110 to 310m2g−1. Chitosan alcogels were found to be the best mould for this replication alleviating the problems associated with the rapid kinetic growth encountered with hydrogels and those of diffusion limitations in dried aerogels. From mechanistic point of view, amino-metal coordination NH2→M (M=Ti, Zr, Al, Sn) and hydrogen bonding between hydroxyl group and oligomeric metal oxide play a pivotal role during the mineralization process.

The beneficial effect of the bifunctional character of the chitosan@titania hybrid in heterogeneous catalysis was elucidated: considering a prototypical Henry condensation, Michael addition, and Jasminaldehyde synthesis, the cohabitation of a basic site (NH(2)) and an acidic site (Ti) in the same reactor provided clear activity and selectivity enhancements, with respect to the monofunctional acidic titania and basic chitosan counterparts.