Search

Stacking faults are two-dimensional planar defects frequently arising in zeolites, modifying their properties and potentially affecting their performance in catalysis and separation applications. In classical zeolite intergrowths, a topologically unique zeolite layer may often pile up after some spatial transformation (lateral translation, rotation, and/or reflection) that may occur in different amounts or directions with about similar probabilities, leading to a difficult to control disorder. Here, we present a new kind of zeolite intergrowth that requires an additional topologically distinct layer rather than a spatial transformation of a unique one. Stacking of the so-called pentasil layers produces the well-known medium pore zeolite MFI. Intercalation in strict alternation of a topologically distinct second layer sandwiched between pentasil layers expands the structure to produce the new extra-large pore IDM-1. Stacking disorder modulates the structural expansion along the stacking direction. The disordered materials have been studied by simulation of the X-ray diffraction patterns using the program DIFFaX and by Cs-corrected highresolution electron microscopy. We show that disorder does not occur at random but in extended domains and can be controlled all the way from MFI to IDM-1 by just varying the concentration of the synthesis mixture., The authors thank funding from the Spanish Ministry of Science, Innovation and Universities, under Projects MAT2015-71117-R (MINECO/FEDER, UE), PID2019-105479RB-I00 and RTI2018-101599-B-C22 (MCUI/AEI/FEDER, UE), the Swedish Research Council (VR), and the Knut and Alice Wallenberg Foundation (KAW). L.A.V. also thanks the Generalitat Valenciana (project PROMETEO/2018/024). A.M. acknowledges the Spanish Ministry of Science (RYC2018-024561-I) and the Regional government of Aragon (DGA E13_20R), the National Natural Science Foundation of China (NFSC-21850410448 and NSFC-21835002), and the Centre for High-resolution Electron Microscopy (CℏEM), supported by SPST of ShanghaiTech University under contract No. EM02161943.

IDM-1 is a new silica zeolite with an ordered and well-defined framework constructed by alternating pentasil layers and interrupted layers, giving rise to an intersecting system of straight medium pores and undulating extra-large lobed pores. This unique structure was solved by rotation electron diffraction and refined against synchrotron powder X-ray diffraction data. Despite the presence of both Si(OSi)3(OH) and Si(OSi)2(OH)2 sites, this new zeolite presents high thermal stability, withstanding calcination even to 1000ºC. The location of defects at specific sites of the structure results in alternating hydrophobic SiO2 and hydrophilic SiO(2-x)(OH)2x intracrystalline regions. This peculiar combination of intersecting medium and extra-large pores and alternating regions of different chemical character may provide this zeolite with unique catalytic properties.

The addition of light ceramic particles to bulk technological materials as reinforcement to improve their mechanical properties has attracted increasing interest in the last years. The metal matrix composites obtained using nanoparticles have been reported to exhibit an improvement of their properties due to the decrease in the size of the ceramic additives to the nanoscale. Additionally, important effects such as the dispersion of the nanoparticles, wettability, and low reactivity can be controlled by the modification of the nanoparticles&rsquo, surface. In this work, we present the preparation of core&ndash, shell MxOm@SiC nanoparticles with different shell compositions. The accurate and reproducible preparation is developed both at the lab and pilot scale. The synthesis of these core&ndash, shell nanoparticles and their scale-up production are fundamental steps for their industrial use as additives in metal matrix composites and alloys. Powder X-ray diffraction and energy dispersive X-ray (EDX) coupled with scanning transmission electron microscopy (STEM) are used to corroborate the formation of the core&ndash, shell systems, whereas line scan-EDX analysis allows measuring the average shell thickness.

[EN] The synthesis of zeolites with new structures and/or improved properties heavily relies on trial and error efforts that are not entirely blind, as the large empirical background accumulated for the last 7 decades can be, to some extent, rationalized and purposefully used to make new materials. The so-called structure-directing factors may be combined to promote (or frustrate) the crystallization of a particular structure. This personal account opens with the concept of geoinspiration, as suggested by Prof. Ruiz-Hitzky, and its application to zeolite synthesis. We then provide a concise overview of structure-direction in the synthesis of zeolites and detail examples, both new and from the literature, on how they can be combined to drive the crystallization towards (or away from) structures displaying particular features., Financial support by the Spanish Ministry of Economy and Competitiveness (MAT2015‐71117‐R and AGL2015‐70235‐C2‐R) is acknowledged. P. L. is grateful to the China Scholarship Council (CSC) for a fellowship and to the Dalian Institute of Chemical Physics for permission to leave. Thanks are also due to Wikimedia Commons and Mr. A. T. Chang for the picture of the hot springs included in the frontispiece.

There is large interest in replicating biological supramolecular structures in inorganic materials that are capable of mimicking biological properties. The use of 5- guanosine monophosphate in the presence of Na+ and K+ ions as a supramolecular template for the synthesis of well-ordered mesostructured materials is reported here. Mesostructured particles with the confined template exhibit high structural order at both meso- and atomic scales, with a lower structural symmetry in the columnar mesophase. Although a chiral space group can not be deduced from X-ray diffraction, analysis by electron microscopy and circular dichroism confirms a chiral stacking arrangement along the c-axis. Guanosine monophosphate based mesophases thus illustrate the possibility for specific molecular imprinting of mesoporous materials by genetic material and the potential for higher definition in molecular recognition., This work was supported by the Swedish Research Council (A.E.G.B.), and L.A.V. thanks the Spanish Government for financial support (project MAT2012-38429-C04) and D.E.L.I for help with the ICP/MS analysis. We are grateful to Prof. Sven Hovmoller (Stockholm University) for advice and helpful discussions regarding electron crystallography and CRISP. We are indebted to Dr. Isabel Correia (Technical University of Lisbon) for her help with circular dichroism measurements.

Calcination in air of GeO 2 zeolites with AST-topology causes reduction of the framework, hence structural destruction, in a notable extension. This is due to the impossibility for the organic cation occluded inside to react with ambient oxygen. As the temperature increases, reoxidation in air of the reduced framework causes episodes of weight-gain. When calcination is carried out in N 2 , weight losses close to 70% imply a loss of Ge due to sublimation of germanium monoxide, GeO. The nature of the organic cation occluded determines the nature and oxidation state of the final residue after calcination in N 2 : for tetramethylammonium the residue is GeO 2 while trimethyl-terc-butylammonium, thanks to its larger C content, yields metallic Ge. Framework organoreduction is not unique to GeO 2 -AST zeolites but also occurs during the calcination in air of other germanium-containing zeolites with larger pore openings., Spanish Ministery of Economy and Competitiveness (Projects MAT2012-31759, MAT2015-71117-R, and MAT2012-38429-C04) and Generalitat Valenciana (Grant PROMETEOII/2014/047)

Zeolite beta crystals (Si/Al = 35) synthesized in fluoride medium were treated in aqueous 0.2 M NaOH solution for mesopore formation by selective extraction of framework silicon. A 16 parallel-batch reactor was used to study the influence of the treatment time and temperature on the physico-chemical properties of the zeolites, which were characterized by ICP-OES, XRD, N2 adsorption at 77 K, SEM, TEM, DRIFTS, and in situ ATR-IR. Alkaline treatment of H-beta within the optimal window of Si/Al ratios identified for other zeolite families leads to extensive silicon extraction at mild treatment conditions. This originates substantial mesoporosity and presumably improved transport, but negatively impacts on the microporous and acidic properties of the resulting sample. Consequently, the alkaline-treated beta zeolites show lower catalytic activity in the acid-catalyzed liquid-phase benzene alkylation than the purely microporous parent material. The relatively low stability of framework aluminum in BEA, compared to MFI and MOR, is detrimental for the controlled mesopore formation by Si dissolution, since aluminum cannot optimally exert its pore-directing role.

Several organic cations derived from the same rigid bicyclic amine 1,3,3-trimethyl-6-azabicyclo[3.2.1]octane have been used as structure-directing agents for the synthesis of pure silica zeolites in the presence of fluoride. The results are rationalized in terms of the varying size and rigidity of the cations. Both concepts were used in defining a large and rigid spiroammonium derivative which afforded the synthesis of the large pore pure silica zeolite ITQ-7. The existence of structural disorder in ITQ-7, which may be controlled through the water/silica ratio of the synthesis mixture, is confirmed by a number of techniques, but high-resolution electron microscopy results ruled out the existence of stacking faults. Thus, disorder in ITQ-7 does not appear to be due to intergrowths and may correspond to the existence of local defects, probably involving double four ring units, causing lattice strain mainly in the ab plane, according to X-ray diffraction simulations.

Although folic acid is essential to numerous bodily functions, recent research indicates that a massive exposition to the vitamin could be a double-edged sword. In this study, the capacity of different caped mesoporous silica particles (i.e. Hollow Silica Shells, MCM-41, SBA-15 and UVM-7) to dose FA during its passage through the gastrointestinal tract has been evaluated. Results confirmed that the four capped materials were capable to hinder the delivery of FA at low pH (i.e. stomach) as well as able to deliver great amounts of the vitamin at neutral pH (i.e. intestine). Nevertheless, the encapsulation efficiency and the deliver kinetics differed among supports. While supports with large pore entrance exhibited an initial fast release, MCM-41, showed a sustained release along the time. This correlation between textural properties and release kinetics for each of the supports reveals the importance of a proper support selection as a strategy to control the delivery of active molecules., Authors gratefully acknowledge the financial support from the Ministerio de Economia y Competitividad (Projects AGL2012-39597-C02-01, AGL2012-39597-C02-02 and MAT2012-38429-C04-01) and the Generalitat Valenciana (project PROMETEO/2009/016). E.P. and M.R. are grateful to the Ministerio de Ciencia e Innovacion for their Grants (AP2008-00620, AP2010-4369). Electron Microscopy Service of the UPV is also acknowledged.

A versatile procedure for anchoring dyes into the pores of multidimensional zeolites by including organic dye precursors in the synthesis gel has been developed. To prove the concept, an aniline-functionalised zeolite Beta was obtained by reaction of triethylorthosilicate (TEOS), tetraethylammonium hydroxide, and N-methyl,N-(propyl-3-trimethoxysilyl)aniline (MPTMSA) in the presence of HF. Further extraction of the structure-directing agents resulted in a highly crystalline, white, functionalised zeolite Beta containing anchored aniline groups. Similar organic functionalised molecular sieves (OFMS) have been explored as novel catalysts, but, as far as we know, OFMS have never been used as precursors for dye-immobilisation or to design new solid-based host systems for selective molecular sensing processes as is reported here. In a second step the solids containing dyes were prepared by reaction of the hybrid material with the appropriate reactives to obtain tricyanovinylbenzene, triphenylpyrylium, azoic, and squaraine derivatives. All these reactions are straightforward and involve electrophilic aromatic substitution or diazotisation reactions at the electron-rich aniline ring. The final dye-functionalised solid materials were isolated by simple filtration and washing procedures and have been characterised by a number of techniques. In all cases the Beta structure of the solid remains unaltered. Among the large number of areas where dye-containing zeolites might be of importance, we were interested in testing their unconventional use as heterosupramolecular hosts in chromogenic protocols. To check their potential use as chemosensors, microporous solids with anchored triphenylpyrilium and squaraine dyes were selected and used as sensors for the chromogenic discrimination of amines. It was found that the response of both solids to amines was basically governed by the three-dimensional (3D) solid architecture that tuned the intrinsic unselective reactivity of the pyrylium dye. By using new solid-state supramolecular chemistry protocols we believe that these, and similar future dye-zeolite hosts, might be promising new sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules.

A new sensory MCM-41-based material for the colorimetric sensing and discrimination of amines has been developed.

A combination of colloidal crystal planarization, stabilization, and novel infiltration techniques is used to build a bimodal porous silica film showing order at both the micron and the nanometer length scale. An infiltration method based on the spin-coating of the mesophase precursor onto a three-dimensional polystyrene colloidal crystal film allows a nanometer control tuning of the filling fraction of the mesoporous phase while preserving the optical quality of the template. These materials combine a high specific surface arising from the nanopores with increased mass transport and photonic crystal properties provided by the order of the macropores. Optical Bragg diffraction from these type of hierarchically ordered oxides is observed, allowing performing of optical monitoring of the different processes involved in the formation of the bimodal silica structure.

A number of techniques (ICP-OES, XRD, SEM, 27Al MAS-NMR, N2 adsorption, NH3-TPD, FTIR of pyridine adsorbed, HRTEM, UV/vis, and EPR) have been applied to characterize the morphology, structure, porosity, acidity, and forms of iron and aluminum in Fe-beta and Fe-ZSM-5 prepared by hydrothermal synthesis and in their products of activation by calcination and steam treatment. The compositions of the zeolite matrices were very similar, with nominal Si/Al and Si/Fe ratios of 36 and 152, respectively. Removal of the template by calcination leads to extensive dealumination in Fe-beta, while having no influence on the state of aluminum in Fe-ZSM-5. Steam treatment was required to massively create extra-framework Al species in the latter sample. In contrast, the sensitivity of framework iron to migration into non-framework positions during postsynthesis treatments and the nature and distribution of the resulting iron species were remarkably analogous in the two zeolite structures. Catalytic tests with direct N2O decomposition and N2O reduction with CO over the steamed iron zeolites confirmed that the microporous matrix intrinsically does not play a decisive role on the activity in these reactions, provided that the resulting forms of iron are similar.

N‐methyl,N‐(propyl‐3‐trimethoxysilyl) aniline was synthesized and used as an intermediate for anchoring dyes on inorganic siliceous supports through electrophilic aromatic substitution reactions.

Magic-angle spinning NMR has been used to probe the local structure of as-made zeolite SFF containing occluded fluoride and N,N-diethyl-2,6-dimethylpiperidinium. The Si−F bond distance has been measured using two methods: variable contact time cross polarization studies (1.74 A) and spinning sideband intensity fitting at relatively slow spinning speeds (1.79 A). Both measurements yield results that are significantly shorter than the internuclear Si−F distance as measured by single-crystal X-ray diffraction (∼1.9 A), which is based on the average positions of the atoms due to disorder and hence does not reflect the true bond distance.

The light hydrocarbon sorption properties of the three 8-ring zeolites, pure silica Si-CHA and ITQ-3 and high silica ZSM-58 (DDR structure type), have been measured and the adsorption rates and adsorption energies of ethene, ethane, propane and propene were determined. Of particular interest is the large difference in the rates of adsorption of propene and propane exhibited by each of these zeolites. For Si-CHA the ratio of the D’s is 43,000 at 30 °C and the activation energies for diffusion of propene and propane are ∼10 and 73 kJ/mol, respectively, indicating that activated diffusion controls the diffusion rate of propane through its 8-rings. The diffusivity decreases in the order ethene ∼ ethane > propene ≫ propane > n-hexane. All three zeolites have potential for the separation of propene from propene/propane mixtures.

Powder and single-crystal X-ray diffraction, combined with MAS NMR measurements, has been used to study the thermal expansion of siliceous zeolite ferrierite as it approaches a second-order displacive phase transition from a low-symmetry (Pnnm) to a high-symmetry (Immm) structure. Below the transition temperature, ferrierite exhibits positive thermal expansivity. However, above the transition temperature a significant change in thermal behavior is seen, and ferrierite becomes a negative thermal expansion material. Accurate variable-temperature single-crystal X-ray diffraction measurements confirm the transition temperature and allow the changes in average atomic position to be followed with temperature. The results from the single-crystal X-ray diffraction study can be correlated with (29)Si MAS NMR chemical shifts for the low-temperature phase. At low temperatures the results show that the positive thermal expansivity is driven by an overall increase in Si[bond]Si distances related to an increase in Si[bond]O[bond]Si bond angles. However, in the high-temperature phase the Si[bond]O[bond]Si angles are approximately invariant with temperature, and the negative thermal expansion in this case is caused by transverse vibrations of the Si[bond]O[bond]Si units.

The structure determination of as-made silica zeolites CHA and FER prepared in the presence of fluoride ions has been accomplished using microcrystal X-ray diffraction at a synchrotron source. In both cases, the location of the fluoride ions has been determined. Fluoride ions are incorporated into small double six-ring cages in the CHA framework, and the organic guests have been located in the larger chabazite cages. In contrast to two previous single-crystal X-ray diffraction studies of as-made siliceous FER prepared in related ways fluoride ions are incorporated into the framework and are found occluded inside small cages in the structure.

Three infrared absorption bands related to fluoride occluded within double four-member ring units of zeolites exist: one corresponds to fluoride itself and the other two are localized vibrations of the cage appearing at adifferent wavenumber depending on the presence or absence of fluoride within the cage. This is demonstrated by comparison of the vibrational spectra of a series of as-made and calcined octadecasil materials containing varying degrees of fluoride and aluminum and is further supported by ab initio quantum chemical calculations.

Several high silica zeolites with three-dimensional systems of large pore channels have been prepared in aqueous fluoride media: Beta, ITQ-7, ITQ-10 and ITQ-14. Pure silica beta can crystallize using up to 17 organic cations considerably different in size, shape, rigidity and C/N ratios. There are clear differences in the powder X-ray diffraction patterns of calcined beta materials prepared with different cations, suggesting structural differences between them. However, this technique cannot be readily used to get further insights into these differences. 19 F MAS NMR spectroscopy shows the existence of fluoride occluded in double four ring cages in most of the different betas, thus demonstrating for the first time the real occurrence in these intergrown materials of polymorphs different from A and B. Double four ring cages are also present in ITQ-7 and in the new ITQ-10 and ITQ-14 zeolites.

An aluminosilicate zeolite with IFR topology can be synthesized in a wide range of Si/Al ratios (Si/Al ≥ 20) using benzylquinuclidinium as a structure-directing agent in the presence of fluoride anions. The phase selectivity of the crystallization depends on both the Al and the water content of the synthesis mixture, and by adjustment of the degree of dilution of the mixture, it is also possible to obtain zeolite Beta. The isomorphous substitution of Si by Al in the IFR framework and the acidity of the calcined zeolite has been confirmed by a number of physicochemical techniques. The calcined IFR material contains acid sites of medium strength with large pores and a large void volume. Partial dealumination occurs during calcination, but N2 and pyridine adsorption experiments do not indicate any pore blocking. The aluminosilicate IFR zeolite contains unusual acid sites that are involved in relatively strong hydrogen bonds. Besides the well-known 1H NMR chemical shift for acid sites at 3.9 ppm and the IR ba...

Variable-temperature single-crystal X-ray diffraction using a synchrotron X-ray source has allowed the mechanism of negative thermal expansion in the pure silica zeolite IFR to be studied in greater detail than was previously possible over the temperature range 30-557 K. The results have allowed the changes in average atomic position with temperature to be measured and the structural features that are important in negative thermal expansion to be identified. The structure of zeolite IFR can be split into two regions: columns of fused rings that expand with temperature and the intercolumn regions, which tend to contract on heating. These competing changes combine to produce a material that contracts parallel to the crystallographic a and b axes and expands in the c-direction. Correlations between zeolite structure and thermal expansivity are also reported.

Powder X-ray and neutron diffraction studies of the calcined siliceous zeolites ITQ-7, ITQ-9 and CIT-5, and the aluminophosphates AlPO4-31 and Mg-doped AlPO4-17 have been carried out as a function of temperature in order to determine their thermal expansivity properties. Of these, ITQ-7, ITQ-9 and MAPO-17 show negative thermal expansivity over a wide temperature range, in common with several other previously studied microporous materials. CIT-5 and AlPO4-31 are anomalous in showing an expansion on heating. A detailed study of CIT-5 highlights the key structural parameters which determine its positive expansivity. From expansivity data currently available on seventeen microporous materials, it is clear that negative thermal expansivity must be considered the norm rather than the exception. Positive expansivity is encouraged by the structure having a relatively high framework density and a one-dimensional channel system.

We present the results of quantitative variable-temperature neutron powder diffraction experiments performed on the OSIRIS instrument at the ISIS facility on the pure silica zeolites chabazite and ITQ-4. Chabazite has been found to be one of the most strongly contracting materials known, with a linear expansion coefficient αv/3 varying from −0.5 × 10-6 to −16.7 × 10-6 K-1 over the temperature range 293−873 K. Full Rietveld refinement has been carried out using three different refinement strategies: free isotropic refinements, refinement using geometrical restraints, and a rigid body refinement. The free isotropic refinement was found to be the most successful. In agreement with previous studies on ZrW2O8 and Sc2(WO4)3 type materials, we suggest that changes in Si−O−Si interpolyhedral bond angles are the driving force for the contraction mechanism. ITQ-4 has also been found to contract over the temperature range 95−510 K, with αv/3 varying from −2.2 × 10-6 to −3.7 × 10-6 K-1 over this range.

Eine neuartige Topologie, ein dreidimensionales System aus grosporigen Kanalen, weist der Zeolith ITQ-7 auf (Struktur siehe Bild). Das Material wurde durch Kombination der strukturdirigierenden Einflusse von Fluoridionen und einem organischen Kation synthetisiert, das dafur konzipiert wurde, die Kristallisation einer Silicatphase mit geringer Dichte zu fordern. Bei ITQ-7 handelt es sich um die bisher am wenigsten dichte kristalline Silicatphase.

Pentacoordinated silicon units, SiO4/2F-, were found by solid-state NMR experiments in various as-made high-silica zeolites (Beta, SSZ-23, ITQ-3, ITQ-4, ZSM-12, Silicalite-1) that are prepared in the presence of fluoride ions as mineralizing agents. The SiO4/2F- units are part of the framework, being connected, through sharing of the four O atoms, with four neighboring tetracoordinated SiO4/2 units. These five-coordinate silicon units balance the charge of the cationic organic structure-directing agent. The 29Si chemical shift of these sites is between −140 and −150 ppm, and the 19F chemical shifts are between −56 and −78 ppm. The zeolites SSZ-23, ITQ-4, and Silicalite-1 show a dynamic motion of the fluoride ions at room temperature which is frozen out at a temperature of 130−140 K. In the case of fluoride motion, the 29Si chemical shifts are between −120 and −150 ppm, indicating an exchange between four- and five-coordinate silicon, which means that the fluoride ions exchange between different framework ...

Recent advances in the synthesis of all-silica and high-silica crystalline molecular sieves in fluoride media, with special regard to low framework density phases, are presented. The fundamental differences between the synthesis in hydroxide and fluoride media with respect to the properties of the materials obtained and the phase selectivity of the crystallization are discussed.

A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials., This work was supported by the Swedish Research Council (Project 2009-4716 AGB). Niklas Hedin acknowledges funding from the Swedish Energy Agency. Luis Angel Villaescusa is grateful for support from the Jose Castillejo Program of the Spanish Ministry of Sport and Education (Project JC2009-00141). The authors thank Y. Cerenius and M. Knaapila (MAX-lab Synchrotron Facitlity, Beamline 1711, Lund, Sweden) for assistance with SAXS experiments and beamline time.

A new silica polymorph of zeolitic nature with large pores, a large void volume and essentially no connectivity defects, is prepared by direct hydrothermal synthesis in a fluoride medium.

The new pure silica polymorph ITQ-4, structure code IFR, Si32O64, monoclinic I2/m a = 18.65243(13), b = 13.49597(8), c = 7.63109(6) A, β = 101.9781(5)°, is a zeolitic material containing a large sinusoidal channel with 12-member ring windows as minimum apertures. Its void volume (0.21 cm3/g) is surpassed only by that of pure silica Beta among the known pure silica polymorphs. The success of the ab initio structure solution from synchrotron powder diffraction data was greatly assisted by the absence of Al and Si−OH defect groups, which generates a very high degree of crystallographic order.

The new pure silica polymorph ITQ-9 has been synthesised and its structure, comprising medium pore channels and cages, has been solved by direct methods using low resolution powder X ray diffraction data.

A novel topology, consisting of a three-dimensional system of large pore channels, is found for the zeolite ITQ-7 (see picture). This material has been synthesized by combining the structure-directing effects of fluoride ions and a new organic cation purposefully designed to promote the crystallization of a low-density silica phase. ITQ-7 is the least dense crystalline silica phase known so far.

Recent advances in the synthesis of all-silica and high-silica crystalline molecular sieves in fluoride media, with special regard to low framework density phases, are presented. The fundamental differences between the synthesis in hydroxide and fluoride media with respect to the properties of the materials obtained and the phase selectivity of the crystallization are discussed.

Electrides are materials in which alkali metals (Li through Cs) ionize to form bound alkali cations and “excess” electrons. The electrons reside in large cavities or channels or both in the host lattice. We report here the first synthesis of thermally stable inorganic electrides with cation-to-electron ratios of 1:1 as in organic electrides. Although alkali metal adducts to alumino-silicate zeolites are well known, the cation-to-electron ratio is generally 3:1 or greater because these zeolites contain alkali cations prior to incorporation of the alkali metal. In this work, two pure silica zeolites, ITQ-4and ITQ-7, with pore diameters of ∼7 A, absorb up to 40 wt % cesium from the vapor phase (even at room temperature). The other alkali metals (except Li) can also be introduced at elevated temperatures. The optical and magnetic properties of the cesium-loaded samples suggest ionization to form Cs+ and e- with substantial electron-spin pairing. The metal-loaded samples are stable to at least 100 °C and are a...

Double four-membered ring (D4R) anionic building units [Ge8O12(OH)8F]− have been synthesised hydrothermally and their structures solved from powder X-ray diffraction.

[EN] Desilication of ITQ-4 (IFR code, 1-dimensional 12-MR channel system of 0.62 nm x 0.72 nm) in aqueous NaOH solutions was practiced in order to produce the zeolite in the hierarchical form, i.e. combining the native micropores with a secondary network of intracrystalline mesopores. The parent material (Si/Al = 32) was synthesized using benzylquinuclidinium as the structure-directing agent in the presence of fluoride anions. The samples were characterized by ICP-OES, XRD, TEM, N(2) adsorption, and FTIR spectroscopy. In a representative treatment, the mesopore surface area of the ITQ-4 experienced a sevenfold increase (from 29 to 206 m(2) g(-1)) upon optimized NaOH post-treatment, whereas the microporosity was reduced by 70% (from 0.20 to 0.06 cm(3) g(-1)). Chemical analysis and infrared spectroscopy of adsorbed pyridine showed that after alkaline treatment the amount of Bronsted acid sites remains practically constant whereas a significant increase in Lewis acid sites was obtained. Infrared studies with adsorbed 2,4,6-collidine concluded that the accessibility of acid sites in the hierarchical zeolite increased substantially due to an increase in the available active sites at the pore mouths of the hierarchical zeolite. (C) 2010 Elsevier B.V. All rights reserved., This work was funded by the Spanish MICINN (CTQ2009-09824/PPQ, PTQ05-01-00980, Consolider-Ingenio 2010, grant CSD2006-0003) and the ICIQ Foundation. JPR is indebted to the Journal Grants scheme of the Royal Society of Chemistry.

Strong negative thermal expansion has been found for the pure SiO 2 zzeolites ITQ-1 (α v =–12.1×10 –6 K –1 ), SSZ-23 (α v =–10.3×10 –6 K –1 ) and ITQ-3 (α v =–11.4×10 –6 K –1 ) from 50 to 500 °C and above.

Mesoporous amino-functionalised solids containing certain dyes have been used as suitable anion hosts in displacement assays for the colorimetric signalling of phosphate in water. Amoros del Toro, Pedro Jose, Pedro.Amoros@uv.es

[EN] Pyrylium-containing mesoporous materials have been used for the chromo-fluorogenic sensing of biogenic amines in an aqueous environment., We thank the Ministerio de Ciencia y Tecnología (MAT2003- 08568-C03-02) for support. F.S. is thankful for a Ramón y Cajal contract. B.G.A. thanks the Generalitat Valenciana and M.C. thanks the Caja de Ahorros del Mediterraneo for a Doctoral Fellowship. A.B.D. thanks the Alexander-von-Humboldt Foundation for a Research Fellowship.

The new pure silica polymorph ITQ-4, structure code IFR, Si32O64, monoclinic I2/m a = 18.65243(13), b = 13.49597(8), c = 7.63109(6) A, β = 101.9781(5)°, is a zeolitic material containing a large sinusoidal channel with 12-member ring windows as minimum apertures. Its void volume (0.21 cm3/g) is surpassed only by that of pure silica Beta among the known pure silica polymorphs. The success of the ab initio structure solution from synchrotron powder diffraction data was greatly assisted by the absence of Al and Si−OH defect groups, which generates a very high degree of crystallographic order.