Modular organic structure-directing agents for the synthesis of zeolites.

Organic structure-directing agents (OSDAs) are used to guide the formation of particular types of pores and channels during the synthesis of zeolites. We report that the use of highly versatile OSDAs based on phosphazenes has been successfully introduced for the synthesis of zeolites. This approach has made possible the synthesis of the elusive boggsite zeolite, which is formed by 10- and 12-ring intersecting channels.

Titania supported gold nanoparticles as photocatalyst.

This Perspective is focused on the photocatalytic activity of gold nanoparticles supported on titania (Au/TiO(2)). Titania is the most widely used photocatalyst, but its limited activity under visible light irradiation has motivated the quest for modified titania materials absorbing visible light. The review starts by justifying how doping with metallic elements is a related strategy, but different, to that leading to the use of Au/TiO(2) in photocatalysis.

Gold(I) catalyzes the intermolecular hydroamination of alkynes with imines and produces α,α',N-triarylbisenamines: studies on their use as intermediates in synthesis.

α,α',N-triarylbisenamines have been efficiently formed and isolated for the first time. The synthesis is based on an unprecedented gold(I)-catalyzed double intermolecular hydroamination between N-arylamines and aryl alkynes. This reaction constitutes a new example of the intriguing behavior of gold as catalyst in organic synthesis.

Multifunctional hybrid organic-inorganic catalytic materials with a hierarchical system of well-defined micro- and mesopores.

Novel layered zeolitic organic-inorganic materials (MWW-BTEB) have been synthesized by intercalation and stabilization of arylic silsesquioxane molecules between inorganic zeolitic MWW layers. The organic linkers are conformed by two condensed silyl-arylic groups from disilane molecules, such as 1,4-bis(triethoxysilyl)benzene (BTEB), which react with the external silanol groups of the zeolitic layers. The hybrids contain micropores within the inorganic layers and a well-defined mesoporous system in between the organic linkers.

Water stable Zr-benzenedicarboxylate metal-organic frameworks as photocatalysts for hydrogen generation.

The Zr-containing metal-organic frameworks (MOFs) formed by terephthalate (UiO-66) and 2-aminoterephthalate ligands [UiO-66(NH(2))] are two notably water-resistant MOFs that exhibit photocatalytic activity for hydrogen generation in methanol or water/methanol upon irradiation at wavelength longer than 300 nm. The apparent quantum yield for H(2) generation using monochromatic light at 370 nm in water/methanol 3:1 was of 3.5% for UiO-66(NH(2)).

Extra-large pore zeolite (ITQ-40) with the lowest framework density containing double four- and double three-rings.

The first zeolite structure (ITQ-40) that contains double four (D4) and double three (D3) member ring secondary building units has been synthesized by introducing Ge and NH(4)F and working in concentrated synthesis gels. It is the first time that D3-Rs have been observed in a zeolite structure. As was previously analyzed [Brunner GO, Meier, WM (1989) Nature 337:146-147], such a structure has a very low framework density (10.

Origin of the different activity and selectivity toward hydrogenation of single metal Au and Pt on TiO2 and bimetallic Au-Pt/TiO2 catalysts.

To improve the activity of Au/TiO(2) catalysts toward hydrogenation without decreasing chemoselectivity, a number of isolated and supported Au, Pt, and Au-Pt nanoparticles have been investigated by means of density functional theory (DFT) calculations. H(2) dissociation on Pt and Au-Pt nanoparticles is considerably faster than that on Au, because H(2) adsorption on Pt atoms is dissociative and no activation barriers are involved. The high chemoselectivity of Au/TiO(2) catalysts does not exist in Pt/TiO(2) catalysts no matter how small the Pt particles are, but can be preserved in Au-Pt/TiO(2) catalysts if the Au/Pt ratio is high enough as to keep Pt atoms isolated and not at the active metal-support interface.

Molecular mobility of nematic E7 confined to molecular sieves with a low filling degree.

The nematic liquid crystalline mixture E7 was confined with similar filling degrees to molecular sieves with constant composition but different pore diameters (from 2.8 to 6.8 nm).

Cu and Au metal-organic frameworks bridge the gap between homogeneous and heterogeneous catalysts for alkene cyclopropanation reactions.

The copper and gold metal-organic frameworks (MOFs) [Cu(3)(BTC)(2)(H(2)O)(3)](n), [Cu(3)(BTC)(2)] (BTC=benzene-1,3,5-tricarboxylate), and IRMOF-3-SI-Au are active and reusable solid catalysts for the cyclopropanation of alkenes with high chemo- and diastereoselectivities. This type of material gives better results than previous solid catalysts while working together with the homogeneous catalysts. These MOFs can help to bridge the gap between homogeneous and heterogeneous catalysis.

Oxygen activation on gold nanoparticles: separating the influence of particle size, particle shape and support interaction.

The adsorption and dissociation of molecular O(2) on extended gold surfaces, isolated gold nanoparticles of different size and shape, and small gold clusters supported on TiO(2) have been investigated by means of DFT calculations. The influence of particle size and morphology on the mode of adsorption and activation of O(2) have been analyzed separately, and it has been found that O(2) dissociation is very sensitive to the arrangement of the gold surface atoms. The control of this variable through catalyst preparation opens one way to improve the activity of gold catalysts.

One pot catalytic conversion of cellulose into biodegradable surfactants.

Cellulose has been directly converted into environmentally friendly alkyl glycoside surfactants in a one pot transformation. By working in ionic liquid media with Amberlyst 15Dry (A15) as catalyst and coupling the rate of cellulose hydrolysis and the rate of glycosidation of the monosaccharides formed with C(4) to C(8) alcohols, it was possible to obtain 82% mass yield of octyl-alpha,beta-glucoside plus octyl-alpha,beta-xyloside.

Modelling active sites for the Beckmann rearrangement reaction in boron-containing zeolites and their interaction with probe molecules.

Theoretical calculations and in situ solid state NMR spectroscopy have been combined to get insight on the nature of the active sites for the Beckmann rearrangement reaction in borosilicate zeolites. The interaction of a B site in zeolite Beta with a series of probe molecules (ammonia, pyridine, acetone and water) has been modelled and the (15)N and (11)B NMR isotropic chemical shift of the resulting complexes calculated and compared with experimental in situ NMR results. This approach has allowed validation of the methodology to model the adsorption on a zeolite boron site of molecules of varying basicity which are either protonated or non-protonated.

Monitoring the interaction of adsorbates on metal surfaces by surface site engineering: the case of ethoxy on Cu, Pd, Ag and Au regular and stepped surfaces.

The interaction of ethoxy with the (111), (100), (511) and (310) surfaces of Cu, Pd, Ag and Au has been studied by means of periodic density functional calculations with the main aim to investigate, in a systematic way, the effect of the coordination number of surface metal atoms directly interacting with the adsorbate on the adsorption properties. The geometry of the adsorbed molecule is only slightly affected by the type of surface but the adsorption energy may change up to 40% on going from the (111) surface with atoms with coordination number of 9 to the (310) one where the coordination number decreases to 6. Analysis of the work function of the different surfaces and of the charge density reveals that the enhancement of the interaction is not due to variations in the charge transfer.

Ceria nanoparticles as heterogeneous catalyst for CO2 fixation by omega-aminoalcohols.

In contrast to gamma-Al(2)O(3), TiO(2), ZrO(2), MgO and Y(2)O(3), CeO(2) is a reusable catalyst for the reaction of CO(2) with omega-aminoalcohols to form cyclic carbamates; the highest yield (68%) was obtained for the preparation of N-alkyl 1,3-oxazolidin-2-ones from N-alkyl ethanolamines.

New chiral ligands bearing two N-heterocyclic carbene moieties at a dioxolane backbone. Gold, palladium and rhodium complexes as enantioselective catalysts.

Biscarbene ligands with two imidazolin-2-ylidene moieties at a chiral dioxolane backbone were used as ligands for gold, rhodium and palladium complexes. All new complexes showed varying degrees of enantioselectivity toward hydrogenation of prochiral alkenes with ees up to 95%.

Extra-large-pore zeolites: bridging the gap between micro and mesoporous structures.

The conditions required to produce zeolites with low framework density and extra-large pores are discussed. Correlations between framework stability and geometrical and topological descriptors are presented. An attempt has been made to rationalize the synthesis of extra-large-pore zeolites in terms of the synthesis mechanism, the directing effect of the organic structure directing agent (OSDA), the framework atoms, and the gel concentration.

A colorimetric sensor array for the detection of the date-rape drug γ-hydroxybutyric acid (GHB): a supramolecular approach.

γ-Hydroxybutyric acid (GHB), a colourless, odourless and tasteless chemical, has become one of the most dangerous illicit drugs of abuse today. At low doses, this drug is a central nervous system depressant that reduces anxiety and produces euphoria and relaxation, sedating the recipient. There is an urgent need for simple, easy-to-use sensors for GHB in solution.

Preparation of symmetric and asymmetric aromatic azo compounds from aromatic amines or nitro compounds using supported gold catalysts.

This protocol describes the aerobic oxidation of aromatic anilines to aromatic azo compounds using gold (Au) nanoparticles supported on TiO(2) as a catalyst. Yields above 98% are achieved under a few bars of oxygen pressure. It should be noted that the use of stoichiometric amounts of environmentally unfriendly reagents, e.

Bifunctional acid-base ionic liquid organocatalysts with a controlled distance between acid and base sites.

Bifunctional acid-base ionic liquid organocatalysts with different distances between the two sites have been synthesised, and their activity for the Knoevenagel condensation has been tested. As has been found to be the case with enzymes, the distance between the acidic and basic sites determines the activity of the bifunctional organocatalyst, and at the optimal distance the reaction rate increases by two orders of magnitude with respect to the purely acidic or basic counterpart organocatalysts. The experimental results have been rationalised through the study of the reaction mechanism of the Knoevenagel condensation between malononitrile and benzaldehyde by means of DFT calculations.

A bifunctional Pd/MgO solid catalyst for the one-pot selective N-monoalkylation of amines with alcohols.

It has been found that a bifunctional metal Pd/base (MgO) catalyst performs the selective monoalkylation of amines with alcohols. The reaction goes through a series of consecutive steps in a cascade mode that involves: 1) the abstraction of hydrogen from the alcohol that produces the metal hydride and the carbonyl compound; 2) condensation of the carbonyl with the amine to give an imine, and 3) hydrogenation of the imine with the surface hydrogen atoms from the metal hydride. Based on isotopic and spectroscopic studies and on the rate of each elementary step, a global reaction mechanism has been proposed.