[γ-1,2-H2SiV2W10O40] Immobilized on Surface-Modified SiO2 as a Heterogeneous Catalyst for Liquid-Phase Oxidation with H2O2

Incorporation of polyoxotungstate complexes in silica spheres and in situ formation of tungsten trioxide nanoparticles

In this paper, we demonstrated a new convenient route for in situ fabrication of well separated small sized WO(3) nanoparticles in silica spheres, through a predeposition of surfactant encapsulated polyoxotungates as tungsten source, and followed by a calcination process. In a typical procedure, selected polyoxotungates with different charges were enwrapped with dioctadecyldimethylammonium cations through electrostatic interaction. Elemental analysis, thermogravimetric analysis, and spectral characterization confirmed the formation of prepared complexes with the anticipated chemical structure. The complexes were then phase-transferred into aqueous solution that predissolved surfactant cetyltrimethylammonium bromide, and finally incorporated into silica spheres through a joint sol-gel reaction with tetraethyl orthosilicate in a well dispersed state under the protection of organic layer for polyoxotungates from the alkaline reaction condition. Transmission electron microscopic images illustrated the well dispersed WO(3) nanoparticles in the size range of ca. 2.2 nm in the silica spheres after the calcination at 465 °C. The sizes of both the silica spheres and WO(3) nanoparticles could be adjusted independently through changing the doping content to a large extent. Meanwhile, the doped polyoxotungate complexes acted as the template for the mesoporous structure in silica spheres after the calcination. Along with the increase of doping content and surfactant, the mesopore size changed little (2.0-2.9 nm), but the specific surface areas increased quite a lot. Importantly, the WO(3)-nanoparticle-doped silica spheres displayed an interesting photovoltaic property, which is favorable for the funtionalization of these nanomaterials.

Immobilization of molecular catalysts in supported ionic liquid phases

In a supported ionic liquid phase (SILP) catalyst system, an ionic liquid (IL) film is immobilized on a high-surface area porous solid and a homogeneous catalyst is dissolved in this supported IL layer, thereby combining the attractive features of homogeneous catalysts with the benefits of heterogeneous catalysts. In this review reliable strategies for the immobilization of molecular catalysts in SILPs are surveyed. In the first part, general aspects concerning the application of SILP catalysts are presented, focusing on the type of catalyst, support, ionic liquid and reaction conditions. Secondly, organic reactions in which SILP technology is applied to improve the performance of homogeneous transition-metal catalysts are presented: hydroformylation, metathesis reactions, carbonylation, hydrogenation, hydroamination, coupling reactions and asymmetric reactions.

Application of Fe2V4O13 as a new multi-metal heterogeneous Fenton-like catalyst for the degradation of organic pollutants

Iron tetrapolyvanadate (Fe2V4O13) was prepared and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) measurement and scanning electron microscopy (SEM). It was found that Fe2V4O13 could effectively catalyse H2O2 to generate active OH; therefore, Fe2V4O13 was employed as a new two-metal heterogeneous Fenton-like catalyst. The decomposition of H2O2 and the degradation of Acid Orange II catalysed by Fe2V4O13 could be well described with a simple pseudo-first-order rate equation between the reaction temperatures of 15 degrees C and 30 degreesC. It was inferred from the reaction activation energy data that the generation of the hydroxyl radical was a control step in a series of reactions for the oxidation of Acid Orange II in the presence of H2O2 and Fe2V4O13. The catalytic activity of Fe2V4O13 towards degradation of Acid Orange II was not only much higher than that of alpha-Fe2O3, V2O5 and FeVO4 but also than that of their mixtures with an identical ratio of Fe and V, such as 2FeVO4 + V2O5 and Fe2O3 + 2V2O5. The high catalytic activity possibly involved a special two-way Fenton-like mechanism and the synergistic activation of Fe(III) and V(V) in Fe2V4O13 towards H2O2.

Assembly of a magnetic polyoxometalate on SWNTs

Recently, the organisation of magnetic molecules on carbon nanotubes has raised much interest due to their possible interesting contribution to molecular spintronics. In this paper, we describe the assembly on SWNTs of a magnetic polyoxometalate encompassing a single cobalt ion (CoPOM) and its isostructural diamagnetic zinc analogue (ZnPOM). The simple magnetic behaviour of CoPOM and the availability of its diamagnetic counterpart render these POM@NTs systems interesting model compounds for the study of molecular electronics devices based on carbon nanotubes and magnetic molecules. The success and rate of the grafting have been investigated by electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, Raman scattering and magnetisation measurements. These characterisations altogether demonstrate the preservation of the structural and magnetic properties of the molecules upon functionalisation and the existence of an electronic communication between the molecules and the nanotubes.

2H-solid-state-NMR study of hydrogen adsorbed on catalytically active ruthenium coated mesoporous silica materials

(2)H solid-state NMR measurements were performed on three samples of ruthenium nanoparticles synthesized inside two different kinds of mesoporous silica, namely SBA-3 silica materials and SBA-15 functionalized with -COOH groups and loaded with deuterium gas. The line-shape analyses of the spectra reveal the different deuteron species. In all samples a strong -OD signal is found, which shows the catalytic activity of the metal, which activates the D-D bond and deuterates the -SiOH groups through the gas phase, corroborating their usability as catalysts for hydrogenation reactions. At room temperature the mobility of the -Si-OD groups depends on the sample preparation. In addition to the -Si-OD deuterons, the presence of different types of deuterons bound to the metal is revealed. The singly coordinated -Ru-D species exhibit several different quadrupolar couplings, which indicate the presence of several non-equivalent binding sites with differing binding strength. In addition to the dissociated hydrogen species there is also a dihydrogen species -Ru-D(2), which is attributed to defect sites on the surface. It exhibits a fast rotational dynamics at all temperatures. Finally there are also indications of three-fold coordinated surface deuterons and octahedrally coordinated deuterons inside the metal.