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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 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.

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 fluoride synthesis route has recently afforded the discovery of several new zeolite structures by combining the structure directing effects of fluoride and organic cations and a systematic screening of synthesis conditions. Here we review our work in this field, highlighting the decisive influence of the water content on the phase selectivity of the crystallizations. Several examples of purposefully designed synthesis are discussed in terms of synthetic strategies and final results. Increasing the size and then the rigidity of the organic cation allowed the discovery of the large pore ITQ-7, while fluoride was successfully used to prevent the crystallization of default phases in the synthesis of the medium and small pore ITQ-13 and ITQ-12 zeolites. After describing the remarkable differences between the hydroxide and fluoride routes during the crystallization as well as on the final materials, we discuss the role of fluoride as catalyst and as structure-directing agent. The tendency of fluoride to get entrapped in small cages of pure silica zeolites points to a mechanism for the F-catalysed condensation of silica markedly different from the OH-catalysed mechanism. An equatorial rather than apical attack of a trigonal bipyramidal species, or a mechanism involving an intermediate in which fluoride bridges the condensing silicate species may account for the observed behaviour. Several practical rules derived from our empirical observations may foster further succesful research aimed to the discovery of new zeolites by this route.

A common misconception is that X-ray diffraction is the best way to measure bond distances. However, in some cases where disorder is present it can yield incorrect answers. The silicon-fluoride bond distance in fluoride-containing zeolite SFF has been measured using two magic angle spinning NMR techniques. Both techniques, variable contact time cross polarization and spinning side band intensity fitting give shorter Si-F bond distances than X-ray diffraction.

The local structure of the [SiO(4/2)F]- unit in fluoride-containing as-synthesized STF zeolite has been experimentally determined by a combination of solid-state NMR and microcrystal X-ray diffraction to be very close to trigonal bipyramidal. Because the fluoride ions are disordered over two sites, the resulting local structure of the [SiO(4/2)F]- unit from a conventional XRD refinement is an average between tetrahedral SiO(4/2) and five-coordinate [[SiO(4/2)F]-, giving an apparent F-Si distance longer than expected. The correct F-Si distance was determined by slow spinning MAS and fast spinning (19)F/(29)Si CP and REDOR solid-state NMR experiments and found to be between 1.72 and 1.79 A. In light of this, the X-ray structure was re-refined, including the disorder at Si3. The resulting local structure of the [SiO(4/2)F]- unit was very close to trigonal bipyramidal with a F-Si distance of 1.744 (6) A, in agreement with the NMR results and the prediction of Density Functional Theory calculations. In addition, further evidence for the existence of a covalent F-Si bond is provided by a (19)F--(29)Si refocused INEPT experiment. The resonance for the five-coordinate species at -147.5 ppm in the (29)Si spectrum is a doublet due to the (19)F/(29)Si J-coupling of 165 Hz. The peaks in this doublet have remarkably different effective chemical shift anisotropies due to the interplay of the CSA, dipolar coupling, and J-coupling tensors. The distortions from tetrahedral geometry of the neighboring silicon atoms to the five-coordinate Si3 atom are manifested in increased delta(aniso) values. This information, along with F-Si distances measured by (19)F--(29)Si CP experiments, makes it possible to assign half of the (29)Si resonances to unique tetrahedral sites. As well as determining the local geometry of the [SiO(4/2)F]- unit, the work presented here demonstrates the complementarity of the solid-state NMR and X-ray diffraction techniques and the advantages of using them together.

Single-crystal X-ray diffraction studies carried out at a synchrotron radiation source have allowed the structure solution and location of fluoride ions inside as-made pure silica zeolites with the IFR and STF framework structures. The local environment of the fluoride has been identified, and unusual ordering of the fluoride ions has been discovered in both cases. The details of the crystal structures are used to suggest structural features that are important in determining the ordering of fluoride ions in zeolites. A mechanism for how the fluoride ordering occurs is suggested for IFR and STF based on the local structure of small cages that make up these zeolites, and the implications for the mechanism of crystal growth are discussed.

Publisher Summary This chapter presents a novel nuclear magnetic resonance (NMR) approach to measure boron/aluminum (B/Al) ordering around structure directing agents (SDAs). The distribution of acid sites is not random, and a local charge-ordering around monoquaternary SDAs is discerned. No such charge ordering is observed for diquaternary SDAs. These methods provide a versatile tool to locate acid sites around the SDA.

An ionically controlled nanoscopic molecular gate has been developed by using functionalized mesoporous materials. The system shows that control of mass transport at nanometric scale can be achieved by using suitable rigid solids and pH-active molecules. The design principle suggests new perspectives in the search of ionically tuned tailored materials and devices with a fine control of mass transport for new applications in fields such as drug delivery, selective removal of toxic species, sensing, or catalysis.

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

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 approximately 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 degrees C and are able to reduce small aromatic molecules such as benzene and naphthalene to the radical anions within the pores of the zeolite.

[EN] The inclusion of squaraine (SQ) dye I into the supercages of zeolite Y (structure code FAU) with a SiO(2)/Al(2)O(3) ratio of 30 (Z30) through a two-step ship-in-the-bottle approach is reported, resulting in the squaraine-containing hybrid material Z30-SQ. Attempts to use the same synthetic procedure on sodium and ammonium Y zeolites were unsuccessful, stressing the importance of the presence of Bronsted acid centres in the Z30 zeolite. The reflectance spectra of Z30-SQ show a maximum in the typical squaraine monomer region at 618 nm and a shoulder at 570 nm. Spectral analyses revealed that the major species are SQ dimers and (tightly adsorbed) SQ monomers and SQ aggregates are only formed to a minor degree. The emission spectrum of Z30-SQ shows a single band at 669 nm. The sensory performance of this material was tested in the presence of volatile propylamine and propylthiol and other volatile organic compounds (acetone, ethanol, dichloromethane, hexane, acetonitrile, ethyl acetate, ethyl ether and acetic acid). The blue Z30-SQ material reacts with the thiol and amine derivatives, resulting in the bleaching of the solid and disappearance of the absorption band in the visible region, but does not undergo spectroscopic changes in the presence of other volatile organic compounds (VOCs). Whereas the reaction with propylamine is irreversible, a partial reversibility was found in the presence of the thiol. Theoretical investigations of the reactivity of I with several VOC molecules at the semi-empirical level reproduced well the experimentally observed reactivity., Financial support from the Spanish Government (project MAT2009-14564-C04-01), the Generalitat Valencia (project PROMETEO/2009/016) and the Innovationsfonds (BAM/Bundesministerium fur Wirtschaft und Technologie) is gratefully acknowledged. J.V.R.L. thanks Generalitat Valenciana for a postdoctoral fellowship.