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Zeolites are becoming more versatile in their chemical functions through rational design of their frameworks. Therefore, direct imaging of all atoms at the atomic scale, basic units (Si, Al, and O), heteroatoms in the framework, and extra‐framework cations, is needed. TEM provides local information at the atomic level, but the serious problem of electron‐beam damage needs to be overcome. Herein, all framework atoms, including oxygen and most of the extra‐framework Na cations, are successfully observed in one of the most electron‐beam‐sensitive and lowest framework density zeolites, Na‐LTA. Zeolite performance, for instance in catalysis, is highly dependent on the location of incorporated heteroatoms. Fe single atomic sites in the MFI framework have been imaged for the first time. The approach presented here, combining image analysis, electron diffraction, and DFT calculations, can provide essential structural keys for tuning catalytically active sites at the atomic level., Financial support is acknowledged from CħEM, SPST, ShanghaiTech in the form of grant no. EM02161943 (A.M., Q.Z., Y.M., and O.T.), NFSC‐21850410448 (A.M.), NSFC‐21835002 (A.M., Y.M., J.Y., and O.T.), basic funding of the MPG (P.L., W.S., and F.S.), Foreign 1000 Talents plan, China (O.T.), CityU‐9610369 (H.H.), 111 project of China B17020 (A.M., J.Y., O.T.), and the Alexander von Humboldt foundation (P.L.). A.M. acknowledges the Spanish Ministry of Science and Innovation (Ramon y Cajal Program RYC2018‐024561‐I).

Defects within zeolites are crucially important for explaining their physicochemical behavior. The UTL zeolite, with a pillared layer structure, has been widely used in zeolite crystal engineering to assemble new structures from its layered structural units, but a fundamental understanding of its defect is lacking. Here, we report a newly synthesized UTL framework zeolite, UTL-DBU, with a commercially available superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a template. Its structure was determined by a combination of three-dimensional electron diffraction tomography and high-resolution (scanning) transmission electron microscopy. Using transmission electron microscopy, two types of defects, stacking disorder and edge dislocation-like planar defect, were discovered. On the basis of the analysis of the electron diffraction and imaging, the layer stacking sequence together with the structural and mathematical models of the microtwinning was successfully built up. Unraveling these defects will provide new insights into the rational design of targeted zeolites utilizing UTL.

Surface-sensitive information on a bulk sample can be obtained by using a low incident electron energy (low accelerating voltage/landing voltage) in a scanning electron microscope (SEM). However, topography and composition contrast obtained at low incident electron energies may not be intuitive and should be analyzed carefully. By combining an Auger electron spectrometer (AES) with a low incident electron energy SEM (LE-SEM), we investigated the SEM contrast carefully by separating the secondary electron (SE) and back-scattered electron (BSE) components with high accuracy. For this, we modified an AES to measure the electron energy in the range of 0–0.6 keV with a sample bias voltage of 0 to −0.3 keV. We could clearly observe reversed brightness of gold and carbon (graphite) in BSE images when the energy of the incident electrons was reduced to 0.2–0.3 keV. In addition, reflected electron energy spectroscopy (REELS) is known to be a tool for chemical state analysis of the sample. We demonstrated that it is possible to study the electron states of graphite, diamond, and graphene by acquiring low incident energy REELS spectra from their surfaces with the newly modified AES. This will be a new method for analyzing the electron states of local areas of a surface.

Hierarchical nanozeolites are highly desired for heavy oil conversion because of their fast mass transfer, good site accessibility, and short diffusion length compared with their conventional counterparts. Here, we provide a facile amino acid-assisted strategy to synthesize hierarchical ZSM-5 (MFI) zeolite nanocrystals by two-step crystallization in a concentrated gel system. Strikingly, each virus-like zeolite nanoparticle with abundant interconnected intracrystalline mesopores is a high-quality single crystal that is defect-free as confirmed by electron diffraction and NMR analysis. By utilizing advanced electron microscopy techniques, we have studied the evolution process of single-crystalline hierarchical ZSM-5 nanocrystals that involves oriented aggregation of protozeolitic nanoparticles formed at low temperature followed by intraparticle ripening at high temperature. The as-prepared hierarchical Ni@ZSM-5 catalysts exhibit superior catalytic performance in hydrodeoxygenation of stearic acid and palm oil.

About 15 years ago, the Ryoo-group described the synthesis of CMK-5, a material consisting of a hexagonal arrangement of carbon nanotubes. Extension of the surface casting synthesis to oxide compositions, however, was not possible so far, in spite of many attempts. Here it is demonstrated, that crystalline mesoporous hollow zirconia materials with very high surface areas up to 400 m2·g-1, and in selected cases in the form of CMK-5-like, are indeed accessible via such a surface casting process. The key for the successful synthesis is an increased interaction between the silica hard template surface and the zirconia precursor species by using silanol group-rich mesoporous silica as a hard template. The surface areas of the obtained zirconias exceed those of conventionally hard-templated ones by a factor of two to three. The surface casting process seems to be applicable also to other oxide materials.

Zeolites are widely used in catalysis, gas separation, ion exchange, etc. due to their superior physicochemical properties, which are closely related to specific features of their framework structures. Although more than two hundred different framework types have been recognized, it is of great interest to explore from a crystallographic perspective, the atomic positions, surface terminations, pore connectivity and structural defects that deviate from the ideal framework structures, namely local structural modulation. In this article, we review different types of local modulations in zeolite frameworks using various techniques, especially electron microscopy (EM). The most recent advances in resolving structural information at the atomic level with aberration corrected EM are also presented, commencing a new era of gaining atomic structural information, not only for all tetrahedral atoms including point vacancies in framework but also for extra‐framework cations and surface terminations., Local structure modulations deviating from ideal framework‐type structures are important fine‐structural features within zeolite frameworks. By using (S)TEM with diffraction and imaging approaches, point, column and planar modulations can be observed in both reciprocal and real space.

Nanoporous crystals are widely studied and used for applications in \(\mathrm{H_{2}}\) storage, \(\mathrm{CO_{2}}\) capture, petrochemical catalysis and many other applications, yet the imaging of their atomic structure has proven difficult because of their radiation sensitivity and the small size of these microcrystals. This chapter describes the development of the new modes of electron microscopy needed to study them, and compares these with traditional methods such as x-ray diffraction. This class of materials has traditionally been dominated by the zeolites and zeotype materials, but has recently been expanded to include meso-/macroporous crystals and other new framework structures (MOFs, ZIFs COFs, etc.). Using different building blocks or units, versatile crystal structures have been synthesized for various applications. Their properties and functions are governed primarily by periodic arrangements of pores and/or cavities and their surroundings with various atomic moieties inside crystals. In this chapter, electron microscopy studies of nanoporous materials are discussed from different perspectives. Special attention is paid to the observation of fine defect structures, through careful analysis of electron diffraction, high-resolution images and spectroscopy data. The experimental conditions for imaging beam-sensitive materials, such as MOFs, are described. The contents have been divided into sections based on the types of materials and their geometric features. Examples of structure analysis of various nanoporous materials are given and discussed. New technical developments and existing challenges are described.

Metal-organic frameworks (MOFs) are attracting considerable attention for their use as both the precursor and the template to prepare metal oxides or carbon-based materials. For the first time in this paper, the core-shell ZIF-8@ZIF-67 crystals are thermally converted into porous ZnO@Co3O4 composites by combining a seed-mediated growth process with a two-step calcination. The designed porous ZnO@Co3O4 composites exhibited the highest photocatalytic activity with an excellent stability for the reduction of CO2 among the commonly reported composite photocatalysts. Their superior photocatalytic performance is demonstrated to be resulting from the unique porous structure of ZnO@Co3O4 and the co-catalytic function of Co3O4 which can effectively suppress the photocorrosion of ZnO.

The structural analysis of silica mesoporous crystals (SMCs) is a key step for understanding their properties, especially toward drug delivery. Although various techniques can be applied, electron crystallography has been proved the most powerful method in the structure solution of mesoporous materials. In this chapter, we will begin with introducing basic crystallography and extend to the 3D structure solution using a set of HRTEM images. Typical examples will also be given to show the structure features of 2D, 3D, cage-type, and hyperbolic surface-type mesostructures. A drug delivery system using SMCs as a reservoir will be given at the end.

The nanoscopic details of the crystal growth of zeolite. A in the presence of the organic modifiers. diethanolmaine (DEA) and triethanolamine (TEA) has been determined using a combination of atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM) coupled with Monte Carlo simulations. Crystallization of zeolite A in the presence of TEA was faster than when the growing solution contained DEA. In addition, the morphology of the final zeolite A crystals depended on the type of organic molecule, with TEA producing crystals bound only by {100} facets and DEA leading to the formation of relatively large {110} faces. These features can be explained in terms of the relative Si/Al in the growing medium and its control due to the different affinity of the organic molecules to Al. In addition, synthesis Si/Al in the growing medium and its contorl due to the different affinity of the organic molecules to Al. In additon synthesis performed at 90 degrees C showed the apperance of {211} facets Careful review of the HRSEM and AFM images, in addition to comparion with the MC simulations, reveals that these are in fact pseudofacets products of the slow dissolution of the metastable zeolite. A crsytals. This proves that the final habit of the LTA crystals can be governed by very small changes in saturation of the growing medium, and control of this parameter can prove advantageous when designing crystals for industrial applications.

Silicoaluminophosphate zeolite SAPO-34 with CHA topology is known as one of the best catalysts for methanol-to-olefin (MTO) conversion. In this work, we demonstrate a facile one-step hydrothermal synthesis of hierarchically macroporous SAPO-34 through the etching effect of hydrofluoric acid. The highly crystalline hierarchically macroporous SAPO-34 is prepared as central-holed rhombohedral crystals with particle size of ca. 5–10 μm that comprise intracrystalline parallel macrochannels of ca. 100 nm. The formation of macroporous structures via in situ growth-etching can be directly imaged by SEM. Strikingly, a particular crystal configuration consisting of eight pyramidal parts has been first observed during the zeolite crystal growth process, which eventually grows to form a perfect rhombohedral shape. The HF etching effect is further elucidated by the analysis of changes of pH values as well as of solid and liquid compositions following the evolution of crystallization. The texture properties, chemical environments of framework atoms, and acidity of the synthesized SAPO-34 are characterized by N2 adsorption/desorption, MAS NMR and NH3-TPD measurements. The hierarchically macroporous SAPO-34 shows larger micropore volume, slightly stronger acid strength, and lower external surface acidity than its conventional counterpart synthesized without using HF. Consequently, the hierarchically macroporous SAPO-34 exhibits excellent MTO catalytic performance, showing much higher selectivity to ethylene and propylene as well as longer lifetime than the conventional counterpart. In comparison with previously reported methods for the generation of hierarchical porosity, this one-step HF-assisted in situ growth-etching synthetic route is simple, straightforward and cost-effective, which offers a new approach to prepare hierarchically porous zeolites with improved catalytic activity.

Through the use of low voltage high resolution scanning electron microscopy (LV-HRSEM) we have studied the fine details of the intricate pore structure of SBA-15. Intrawall pores and deviations from the ideal and uniform cylindrical pores are clearly observed, and we report for the first time the direct observation of “plugs” in the pores. N2-sorption measurements confirm their existence. LV-HRSEM provides an opportunity to quantify the frequency of occurrence of plugs within the pore structure. The rate of mesophase formation, followed with in situ small angle X-ray scattering (SAXS) under different solvent conditions, is shown to have a significant influence on the development of plugs and how frequently they occur. We suggest a mechanism explaining the existence of the plugs, providing means for a better understanding and control over material properties.

An ordered mesoporous MFI zeolite material (Meso-MFI) was prepared by using CMK-type mesoporous carbons as a hard template. The Meso-MFI exhibits both structural and adsorption differences compared to the conventional bulk MFI zeolite. To study the argon (Ar) adsorption process in Meso-MFI, an in situ gas adsorption powder X-ray diffraction (XRD) analysis was performed using synchrotron X-ray source. Structural rearrangement of the mesoporous MFI zeolite upon Ar adsorption at low temperature (83 K) was intensively studied together with Ar adsorption process in Meso-MFI. We observed that a structural transition of the Meso-MFI zeolite framework from monoclinic (P21/n) to orthorhombic (Pnma) occurred at around 126 Pa at 83 K. Positions of Ar atoms are determined as a function of the Ar gas pressure through Rietveld refinement of powder XRD data. Ar atoms are observed at straight channels, sinusoidal channels, and the intersection of these channels at low pressure. As gas pressure increases, Ar atoms in the ...

A new method to produce SEM cross sections was used to analyze coated and creased samples. It was found that the binder surrounded the smaller particles leaving the large pores around the larger pi ...

A new approach for observing fine structures of novel thin, nanostructured materials called through the lens system (TTLS) is employed to observe interesting features on a variety of new, catalytically-important, hierarchically porous rattlespheres.

The crystallization of zeolite A by the verified synthesis method was studied by means of high-resolution scanning electron microscopy (HRSEM) and atomic force microscopy (AFM). These methods show ...

The crystallization of LTA zeolite under a hydrothermal synthesis condition that contained a quaternary ammonium-type organosilane surfactant was studied with X-ray powder diffraction (XRD), high-r ...

A novel methodology was successfully developed to expand the structure of zeolitic lamellar precursors through molecular alkoxysilylation. The method has been applied to PREFER (lamellar precursor of ferrierite). As a result, a novel crystalline interlayer expanded zeolite named as IEZ-FER (IEZ is the abbreviation of interlayer expanded zeolite) with enlarged distance perpendicular to the layer was synthesized through interlayer molecular alkoxysilylation. In this paper, the structure of IEZ-FER has been comprehensively studied by various means such as electron diffraction, high-resolution electron microscopy (HREM) and structure modeling. Our studies provide evidence that IEZ-FER preserves the pentasil layers corresponding to that found in the known three-dimensional (3D) FER zeolite, but it also shows a distinct expansion of the layer spacing (∼5 A). The newly formed channel system is distinct from that of the known 3D FER structure,which has 8-membered ring (MR) and 10MR pores along the [010] and [001]...

The process of gas adsorption on mesoporous crystals can be explored by in situ synchrotron powder X-ray diffraction (XRD) that provides direct information about the distribution of adsorbate with the pore channels. We presented a rigorous theoretical framework for interpretation of the in situ XRD data based on the novel quenched solid density functional theory (QSDFT) model of adsorption on mesoporous materials. QSDFT accounts for the molecular level roughness of the pore walls that is shown to be one of the major factors affecting both the adsorption isotherms and the XRD patterns. Drawing on the example of Ar adsorption in pores of MCM-41, we demonstrate that, using the intermolecular potentials established from the adsorption data and the structural parameters (pore size and roughness) determined from the XRD data, the QSDFT model describes the in situ synchrotron powder XRD intensities on a quantitative level. The QSDFT model provides an opportunity for a unified interpretation of adsorption and XRD...

The preparation of bioceramics with ordered mesoporous structures is of importance for biomedical technology, for the design of bone and dental grafts with regeneration purposes. Here we demonstrate that hexagonal mesoporous SiO2−CaO−P2O5 bioglasses (MBG) with high calcium content are the first known bioceramics that exhibit amorphous calcium phosphate (ACP)−octacalcium phosphate (OCP)−calcium deficient carbonatehydroxyapatite (CDHA) maturation as biomineralization governing mechanism in simulated body fluid (SBF), similarly to the in vivo biomineralization process. The unique characteristics of hexagonal MBGs lead to a local acid pH at the bioceramic surface that allows the formation of metastable OCP. Besides, 3D cubic MBG has been also synthesized, exhibiting higher surface area and porosity. The 3D reconstruction carried out by electron microscopy evidence a 3D bicontinuous network comprising a pair of rods mutually intertwined, creating the pore system available in three dimensions. This 3D pore syst...

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.

Right- and left-handed excess chiral mesoporous silica nanotubes with a helical channel in the wall have been formed by the self-assembly of an achiral surfactant sodium dodecyl sulfate (SDS) in the presence of (R)-(+)- and (S)-(−)- 2-amino-3-phenyl-1-propanol ((R)-(+)- and (S)-(−)-APP) chiral molecules. Transmission electron microscopy combined with computer simulations confirmed the presence of ordered chiral channels winding around the central axis of the tubes of ∼100 nm inner diameter. Furthermore, it has been found that these have been produced through a specific crystallization route that hollows out the chiral mesoporous silica rod, which is different from the tube synthesis pathways reported previously. The enantiomeric excess ee of chiral mesoporous silica has been increased from 0 to a maximum value of 32% with increasing (R)-(+)-APP/SDS molar ratios from 0 to 0.8.

Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles., The selective growth of mesoporous gold thin films with control over the porosity is a challenging task. Here, the authors report a soft-templating method allowing the growth of tunable, mesoporous gold films and examine their optical properties

A mesoporous silica AMS-10 with novel bicontunuous cubic Pn-3m symmetry was synthesized and chracterized by electron crystallography.

A series of ordered mesoporous SiO2−CaO−P2O5 sol−gel glasses which are highly bioactive has been synthesized through evaporation-induced self-assembly in the presence of a nonionic triblock copolymer, EO20PO70EO20 (P123), template. By keeping constant the SiO2 + P2O5/P123 ratio, the influence of the CaO precursor, Ca(NO3)2·4H2O, on the mesostructure has been determined. After calcination at 700 °C, ordered mesoporous glasses are obtained, showing structures that evolve from 3D-cubic to 2D-hexagonal when the CaO content increases. The mesoporous glasses are highly bioactive compared with conventional ones, due to the increased textural characteristics supplied by the template. The bioactivity tests point out that the surface area, porosity, and 3D-structure become more important than chemical composition during the apatite crystallization stage in these materials, due to the very high textural parameters obtained.

The pore shape and size of MCM-41 were studied analytically by comparing the observed powder X-ray diffraction intensities with that derived from the MCM-41 crystal structure models, with two different pore shapes, a hexagon and a circle. The powder diffraction patterns from the as-synthesized and the calcined MCM-41 were measured by a synchrotron radiation at SPring-8, Japan. The MCM-41 structure with circular and hexagonal pore shapes explains well for the as-synthesized and the calcined MCM-41 crystals, respectively. The pore size and boundary obtained by this approach agree with those obtained from an N2 gas adsorption measurement combined with the Fourier synthesized density map.

The synthesis and crystallization mechanism of various mesoporous molecular sieves with varying morphology have been studied by the methods such as X-ray diffraction (XRD), scanning-electron microscope (SEM), elemental analyses and N2 adsorption–desorption. By adjustment of the synthesis conditions, two types of mesoporous materials with highly resolved XRD patterns and particular morphologies were obtained using cetyltriethylammonium bromide (CTEABr) in the presence of HCl. The g value of lyotropic crystal mesophases was decreased with heating, which led to formation of larger curvature mesophases. The large g value lyotropic crystal mesophases were formed with increase in the surfactant concentration and with decrease in the Si/surfactant ratio.

High-resolution electron microscopy (HREM) has been used to image the surface structure of nano- and micrometer-sized synthetic crystals of zeolite-Linde-L (LTL). Columnar holes and rotational, nano-sized, wheel-like defects were observed within the crystals, where the hole has a minimum size equal to that of the rotational defect. Predictions of surface structure from atomistic computer simulation concur with the observations from HREM and provide insight into the crystal growth mechanism of perfect and defective LTL. Analysis of the energetics of the formation of rotational defect structures reveals that the driving force for defect creation is thermodynamic and furthermore, the rotational defects could be created in high concentrations. Formation of a columnar hole is found to be slightly energetically unfavourable and therefore we speculate that the incidence of both rotational and nano-sized vacancy defects is strongly dependent on kinetic factors and reaction conditions. The morphology of nano- and microcrystalline LTL is contradistinct and we use insights from simulation to propose an explanation of the disparity in crystal shape.

Here we describe studies of the fine structure of zeolites by TEM started at Cambridge in 1982. These include investigations of coincidence boundaries in LTL, the surface structures of FAU and EMT, the surface structures of LTL and supported metal clusters and the structural relation between MFI and MEL. These, combined with present studies of mesoporous crystals and nanostructured materials demonstrate the strength of electron microscopy in this field of material science.

The authors are grateful to Messrs Makoto Watanabe (Hitachi Science System) and Yasushi Nakaizumi (Hitachi High-Technologies Corporation) for taking scanning electron micrographs. S.C. thanks Dr. M. Yudasaka (ICORP-JST) for giving advise and comments.

Recently, we have developed a new electron crystallography (EC) method for study of three dimensional (3D) structures of silica-mesoporous materials, and the 3D-structural solutions of MCM-48 and SBA-1, -6, and -16 were briefly reported. The method gives a unique structure solution through the Fourier sum of the 3D-structure factors, both amplitudes and phases, which are obtained from Fourier analyses of a set of high-resolution electron microscope (HREM) images. The method was fully described in an application for structure analyses of two MCM-48 crystals with different crystal morphologies. Little structural difference was observed between the two crystals, although small differences in the structure factors were observed. The space group of MCM-48 was determined to be Ia3d, and the wall surface of the two crystals followed exactly the periodic minimal surface of gyroid (G). The wall separated two interpenetrating and noninterconnecting channel systems with different chiralities. After structural analy...

Three linear diquats of different lengths (consisting of two quinuclidinium groups linked by a chain of 8, 6 or 4 methylene groups) have been used as structure directing agents in the synthesis of silica zeolites in the presence of fluoride anions. Phase selectivity changes induced by changes in the concentration of the crystallizing mixture or by the addition of Al have been investigated. For the longest diquat only Beta and ZSM-12 were detected by X ray diffraction in the product, with Beta being favoured at high concentrations, low temperatures and short crystallization times. As the length of the chain decreases other phases, in addition to Beta and ZSM-12, appear: ZSM-5 (for the diquat of intermediate length) and ITQ-8, ITQ-10 and ITQ-14 (for the shortest diquat). ITQ-8 is most likely a layered silicate, while ITQ-10 and ITQ-14 are stable zeolites with intergrown structures related to the zeolite Beta family. Notably, ITQ-14 was found to consist of crystallites with the so far hypothetical “structure C” overgrown on standard zeolite Beta crystals. The phase selectivity effect of introducing Al into the gel is generally similar to the effect of decreasing its water content. However, with the longest diquat a different zeolite, Nu-87, crystallized in the presence of Al in a wide range of Si/Al ratios (25–200) but not for pure silica compositions or for the shortest diquats.

No other single instrument rivals the electron microscope in the wealth of structural (atomic, nanoscopic, mesoscopic and microscopic), topographic and electronic information that it provides in the characterisation of solid catalysts such as those used commercially or for laboratory trials and model studies. After a brief update on the significance of recent dvances in technique which, inter alia, allows electron crystallography to be used as freely—and on much smaller specimens—as X-ray crystallography, the veracity of the above claims is illustrated by a number of specific examples. These include: (a) pin-pointing the location and topography of nanoparticle catalysts; (b) constructing element maps (and compositional distributions) of solid catalysts; (c) elucidating the nature of intergrowths (coherent, recurrent and random) of closely similar structures within a supposed new catalyst; and (d) identifying atoms (or small groups of atoms) of high atomic number supported on large-area solids.

Using monocrystalline silicon slice (MSS) as the silicon source, a high-quality zeolite MFI giant single crystal with the average size of 2 mm × 1 mm × 1 mm has been synthesized in the presence of F-. Experimental results show that the MFI giant single crystal in this work has a much larger size and better morphology than crystals synthesized in the traditional systems. The XRD patterns, the microphotographs, the crystallization curves, the thermogravimetric (TG) and differential thermal analysis (DTA), and the N2 adsorption measurements show that MSS is an effective silicon source for the synthesis of high-quality MFI giant single crystals. Meanwhile, strong visible photoluminescence (PL) of the Si-encapsulated zeolite MFI giant crystal at both room temperature and 10 K indicates that such a MFI giant single crystal is a fine host for the preparation of functional materials.

AlPO4-11 nanocrystals, 0.05×0.08 μm in size, were synthesized by optimizing the following chemical parameters: the crystallization temperature and time, the H2O content, the molar ratio of phosphorus to organic template (P2O5/R), and the HF content. The products were characterized by powder X-ray diffraction and scanning electron microscope. AlPO4-11 nanocrystals could not be obtained by optimizing only the crystallization temperature, time and the water content, but obtained by optimizing the molar ratio of P2O5/R, the organic template, and the HF content.

Crystallisation pathways in framework materials, such as zeolites, have been monitored using a combination of atomic force microscopy, high-resolution electron microscopy and modelling. The principle conclusions of this study is that many open-framework crystals grow via a layer growth mechanism. The layers have a thickness which is related to the unit cell parameter in the direction of growth. The development of each layer can be sub-divided into a number of individual growth processes including nucleation of a new layer (or terrace), growth at edge sites and kink sites. Modelling of atomic force micrographs yields relative probabilities for these individual growth processes and reveals that growth at kink sites is favoured with nucleation of new terraces the slowest process. The layer mechanisms proposed explain the incorporation of defects in framework structures and further elucidate the role of structure directing agents.

Crystal-growth phenomena in open-framework microporous materials are explored using a combination of atomic force microscopy, high-resolution electron microscopy and modelling. Analogies are drawn between these open-framework systems and dense phase structures. In particular we discuss the role of organic structure-directing agents, commonly known as templates and suggest a new philosophy for predicting suitable molecules. We also discuss the role of defects in the crystallisation of open-framework materials and the effect of crystallisation processes on the incorporation of defects and intergrowths.

The preparation of macro–micro bifunctional porous materials has been accomplished by a well-controlled, vacuum-assisted technique. Monodisperse polystyrene latex spheres were ordered into close-packed arrays by slow sedimentation, allowing a high flux of water through the interstices between latex spheres. Zeolite LTA, FAU, LTL, BEA, MFI and Si-MFI nanocrystals, synthesized by hydrothermal procedures, permeated the interstices of latex spheres under the driving force of flowing water. After drying and calcination at 500°C, both the latex spheres and zeolite structure-directing molecules were removed, followed by the formation of products consisting of both crystalline micropores and periodic, interconnected networks of submicron macropores. XRD, SEM, TEM, IR, TG/DTA, ICP and N2 adsorption–desorption measurements were performed to monitor the preparation and to characterize the properties of the macro–micro bifunctional porous materials. The materials presented in this paper combine the benefits of both the micropore and macropore regimes. They could potentially improve the efficiency of both separation and catalysis of zeolites.

This paper is concerned with the role of organic structure-directing agents during competitive synthesis of zeolite intergrowths. The system chosen for study is that of the intergrowth between the cubic (FAU) and hexagonal (EMT) polymorphs of zeolite Y. These two polymorphs can be synthesised using crown ether templates and it has been previously shown that mixtures of crown ethers produce intimate intergrowths of FAU and EMT. It was also previously suggested that concentration gradients of crown ethers at crystal growing surfaces are responsible for an oscillation of the structure between the two phases rather than a completely random intergrowth. In this current work we have made a detailed study of comparative syntheses, both stirred and static, in order to assess the role of diffusion of structure-directing agents to a growing crystal surface. Using a combination of high-resolution electron microscopy, X-ray diffraction and modeling we have established that diffusion-limited transport of structure-directing agents to growing crystal surfaces is an important factor controlling the final product. We also establish the “true” threshold concentration of crown ethers to synthesise each individual phase. This work has consequences for our general understanding of structure-directed growth of microporous crystals.

The effect of different structure-directing agents (SDAs) on the nucleation of MTW (the structure code for ZSM-12 recommended by the International Zeolite Association Structure Commission) is shown by means of transmission electron microscopy (TEM). A loose-fit SDA interacting only weakly with the framework seems to have pore-filling character only and results in large domains with rather perfect ZSM-12 framework structure. Conversely, a more tight-fit SDA interacts markedly with the framework during the crystallization and causes simultaneous growth of small domains as well as frequent twinning. By comparison of simulated and experimental electron diffraction patterns as well as high-resolution transmission electron microscopy (HRTEM) images, the proposed crystal structure of ZSM-12 is substantiated. The presence of an organic SDA confined in the one-dimensional channels is established in HRTEM images obtained from calcined as well as as-synthesized specimens. This result is corroborated not only by corr...

Zeolites are one of the most important materials currently used in the petroleum industry for a wide variety of catalytic transformations. However, they are increasingly being considered for other applications such as for designing quantum-confined materials in their spaces. With such applications in mind, precise characterisation of zeolites and related porous materials has never been more necessary. Here we show how electron diffraction coupled with high-resolution imaging can reveal the detailed fine structure in both the bulk and at the surface of these materials. A variety of case studies are considered which include ETS-10, FAU, LTL and FSM-16.

High-resolution electron micrographs and X-ray powder diffraction patterns for the mesoporous material FSM-16 and for silicate organic complexes derived from the layered polysilicate kanemite are presented. HREM studies reveal information about the formation mechanism at the nanometer length scale, and X-ray powder diffraction data provides information about the averaged structure in the samples. It is demonstrated that the FSM-16 material is formed from the layered silicate kanemite through making a domain structure with hexagonal symmetry by condensation of silicate, which might be derivative of kanemite sheets, and the 'folded sheet mechanism' should be modified.

The formation of large zeolite single crystals can be achieved by controlling the factors affecting the crystallization process. A review of several major strategies for the synthesis of large zeolite single crystals based on our studies is presented. Through the addition of a nucleation suppresser to the reaction mixture and optimization of the synthesis conditions, pure uniform large single crystals of LTA and FAU(X) are obtained. Large single crystals of MOR, MFI and BET are prepared using the ‘two-silicon source’ technique. In the presence of fluoride, a large number of single crystals including silicalite-I, B-, Ti-MFI, AlPO 4 -5, -11, -34. GaPO 4 and InPO are promoted. It is found that a clear homogeneous solution favors the crystallization of large single crystals of AFI. The alcoholic synthesis route has proved to be one of the most effective ways to obtain large single crystals of some zeolites and metal phosphates.

Termination structures of surfaces of zeolite L crystals are studied by high-resolution electron microscopy (HREM). By comparing observed HREM images with simulated ones based on some ideal models ...

Recently, a pure MEL type silica zeolite was successfully synthesized by one of the authors. Boron atoms were incorporated into its framework structure by using similar synthesis conditions with gels containing boron in an effort to confer catalytic activity. The nature of crystal faults in the borosilicate-MEL zeolite (B-MEL) was studied using transmission and scanning electron microscopy (TEM and SEM). Electron diffraction (ED) patterns show characteristic diffuse streaks along the [100] and [010] directions. From the analyses of both the diffuse streaks in ED patterns and high-resolution electron microscopy (HREM) images, it was determined that the framework structure of the B-MEL crystal has many planar faults that are parallel to the (100) and (010) planes. The local structure of the planar faults can be interpreted by the intergrowth of the MFI type structure, and a model of the growth process for the B-MEL is speculated from the results.

Microporous crystal of the aluminophosphate analogue with levyne structure (AlPO4-35) were successfully synthesized in the presence of HF using tropine hydroxide as an organic template. Generally, under a starting composition of Al2O3:P2O5:1.5 Tropine:HF:200 H2O, the crystallization product is the microporous material AlPO4-5; a pretreatment at 100 °C for 10 h leads to the formation of the aluminophosphate analogue with levyne structure (AlPO4-35), although the starting composition is the same. Observation of the pretreatment at 100 °C by X-ray powder diffraction showed that poorly crystalline AlPO4 · 2H2O (metavariscite/variscite) plays an important role as reactive intermediate in the synthesis of microporous AlPO4-35.