"Space—the final frontier." This preamble to a well-known television series captures the challenge encountered not only in space travel adventures, but also in the field of porous materials, which aims to control the size, shape and uniformity of the porous space and the atoms and molecules that define it. The past decade has seen significant advances in the ability to fabricate new porous solids with ordered structures from a wide range of different materials. This has resulted in materials with unusual properties and broadened their application range beyond the traditional use as catalysts and adsorbents. In fact, porous materials now seem set to contribute to developments in areas ranging from microelectronics to medical diagnosis.

Ordered porous materials for emerging applications

Chemical modification of silica surface by immobilization of functional groups for extractive concentration of metal ions.

This review paper deals with proven and potential applications of mesoporous molecular sieves in catalysis. In addition to introduction and conclusion, the text is divided into two parts, respectively, dedicated to the design of solid catalysts and catalyst supports and to some relevant examples of catalytic processes.

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Perspectives in catalytic applications of mesostructured materials

IR spectroscopy in catalysis

Thisreviewdiscusses preparationanduseofthesyntheticlayerednanoparticlesinpolymermatrices, i.e., in the polymeric nanocomposites (PNCs). Several types of synthetic or semi-synthetic layered materials are considered, namely the phyllosilicates (clays), silicic acid (magadiite), layered double hydroxides (LDHs), zirconium phosphates (ZrPs), and di-chalcogenides. The main advantage of synthetic clays is their chemical purity (e.g. absence of amorphous and gritty contaminants, as well as arsenic, iron, and other heavy metals), white to transparent color that assures reproducibly of brightly colored products, as well as a wide range of aspect ratios, p ¼ 20 to £6000. Several large scale production facilities have been established. The synthetic clay and LDH industries are oriented toward big volume markets: catalysis, foodstuff, cosmetics, pharmaceuticals, toiletry, etc. The use of these materials in PNCs is limited to synthetic clays and LDHs, mainly for reinforcement, permeability control, reduction of flammability, and stabilization, e.g. during dehydrohalogenation of chlorinated macromolecules. The use of lamellar ZrPs and di-chalcogenides is at the laboratory stage of functional polymeric systems development, e.g. for electrically conductive materials, catalysts or support for catalysts, in photochemistry, molecular and chiral recognition, or in fuel cell technologies, etc. Copyright # 2007 John Wiley & Sons, Ltd.

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Synthetic, layered nanoparticles for polymeric nanocomposites (PNCs)

Phosphotungstic acid (HPWA)–silica composites were synthesised upto 80 wt.% HPWA loading both by conventional impregnation and sol–gel incorporation techniques. The samples were characterised by BET, XRD, NMR, FT-IR and TG. A comprehensive study on the effect of HPWA loading on the acidity has been performed using pyridine adsorption, NH3 TPD and a catalytic test reaction. The samples containing 50 wt.% HPWA showed the best overall performance. Although, the acidic properties of the impregnated catalysts were superior to their sol–gel counterparts, stability measurements (XRD, FT-IR and test reaction) performed before and after washing the samples with H2O/EtOH mixture have unambiguously proved that the sol–gel derived composites are more suitable for the purposes of heterogeneous catalysis.

Synthesis, characterisation and catalytic applications of sol–gel derived silica–phosphotungstic acid composites

29Si and 13C MAS-NMR characterization of surface modification of micelle-templated silicas during the grafting of organic moieties and end-capping

The surface of micelle-templated silicas (MTS) was functionalized by silylation with 3-chloropropyltriethoxysilane in anhydrous toluene. The modified sample (Cl–MTS) was then end-capped by vapor phase treatment with hexamethyldisilazane (HMDZ), which led to the AZA–Cl–MTS sample. The textural properties of the support were preserved during the different modifications. A comparison of 29Si MAS-NMR spectra of Cl–MTS with those of the parent support (MTS) showed that silylation occurred through nucleophilic attack at silicon atoms located in the hydrophobic part of the surface. This mechanism differed from the sol-gel mechanism, which involves H-bonded silanol groups during silylation in polar or aqueous solvent. Residual silanol groups of the Cl-MTS surface were not totally end-capped during HMDZ treatment. This result is explained by the steric hindrance of the trimethylsiloxane groups, which would act as umbrellas that protect the surrounding silanol groups.

29Si and 13C MAS-NMR characterization of surface modification of micelle-templated silicas during the grafling of organic moieties and end-capping.

29Si, 27Al and 23Na MAS NMR techniques are used to investigate Y-type zeolites before and after reaction with CFCs (CCl4, CCl3F, CCl2F2, CClF3, CF4) and a HCFC (CHClF2). 27Al NMR spectra prove the existence of an intermediate aluminum species (distorted tetrahedral or pentacoordinated) at about 30 ppm starting from tetrahedral framework position and leading to octahedral extra framework position during the dealumination process. The presence of C–Cl bond is essential for the decomposition of CFCs, but two chlorine atoms are required for the formation of effective phosgene intermediate. HY zeolite is the least resistant to the proposed CFC compounds. On the bases of multinuclear NMR results a mechanism is given for the decomposition of CFCs. The reaction of the HCFC with zeolites follows a different mechanism. In this reaction the Y-type zeolites with basic centers are also active.

Solid state MAS NMR investigation of Y-type zeolites reacted with chlorofluorocarbons

https://pure.fundp.ac.be/ws/files/989458/56309.pdf

P. Lentz

Papers

Synthesis, characterisation and catalytic applications of sol–gel derived silica–phosphotungstic acid composites

29Si and 13C MAS-NMR characterization of surface modification of micelle-templated silicas during the grafting of organic moieties and end-capping

29Si and 13C MAS-NMR characterization of surface modification of micelle-templated silicas during the grafling of organic moieties and end-capping.

Solid state MAS NMR investigation of Y-type zeolites reacted with chlorofluorocarbons

Synthesis and characterization of Fe- and (Fe,Al )-MCM-22 zeolites