Structure Solution and Defect Analysis of an Extra-Large Pore Zeolite with <b>UTL</b> Topology by Electron Microscopy

Li, Junyan; Zhang, Chuanqi; Jiang, Jiuxing; Yu, Jihong; Terasaki, Osamu; Mayoral, Álvaro

doi:10.1021/acs.jpclett.0c00551

Cited by 7 publications

(4 citation statements)

References 37 publications

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“…These methods include dynamical refinement of electron diffraction tomography data, [ 174 ] powder XRD and aberration corrected scanning transmission electron microscopy, [ 175 ] and a combined approach involving 3D electron diffraction tomography and high‐resolution scanning transmission electron microscopy. [ 176 ] These developments allow for unprecedented identification of the state of zeolitic materials at the atomic level, and therefore are important steps toward the goal of rational design of targeted zeolites.…”

Section: Discussionmentioning

confidence: 99%

Zeolite (In)Stability under Aqueous or Steaming Conditions

et al. 2020

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zeolites, modification of zeolite acidity for use as fluid catalytic cracking (FCC) catalysts or even for the preparation of novel zeolite frameworks. [1] Considering the significance of zeolite applications at the industrial level, a thorough understanding of zeolite (in)stability under aqueous conditions has been identified as a very important problem in catalysis and zeolite science. Zeolite (in)stability in water or under steaming conditions has been investigated by a number of experimental techniques, in particular magic angle spinning (MAS) NMR, IR, powder X-ray diffraction (PXRD), calorimetry and adsorption. Experimental studies have often been augmented by computational modeling and a large number of relevant theoretical papers can be found in the literature. While the main focus of this review is on reactive interactions of water with zeolites, it is also important to review the most important observations obtained for nonreactive water adsorption in zeolites. It is not surprising that all-silica zeolites, which exhibit negligible water uptake are stable even under conditions where Alcontaining zeolites lose crystallinity: the effective framework hydrolysis can only take place when sufficient water is present in the zeolite channel system. The amount of water inside the zeolite channels depends critically on the concentration of heteroatoms and/or framework defects, such as silanol nests, which show much higher affinity toward water than hydrophobic SiOSi bridges. Zeolite hydrophobicity increases with increasing Si/Al ratio and incomplete pore filling by water is commonly observed for zeolites with high Si/Al at standard pressure. It has been suggested already in the 1950s by Young that water can only adsorb on surface silanol groups, while the parts of the silica surfaces formed by SiOSi bridges are hydrophobic. [2] Both water adsorption in zeolites and zeolite (in)stability under aqueous conditions depend on the zeolite composition (Si/Al ratio, charge-compensating cations, and defect concentration in particular). Our primary goal is to review the most critical aspects of zeolite (in)stability for a broad range of temperature and partial water pressure (p 0), focusing on the framework zeolite composition (Si/Al ratio and presence of Ge, Sn, and Ti heteroatoms) and defect concentration. Zeolites (in)stability in water is discussed for increasing extent of framework degradation, starting from the nonreactive interaction with water, reversible hydrolysis of TO bonds, mild zeolite demetallation, mesopore formation, and total amorphization (Figure 1). Zeolites are among the most environmentally friendly materials produced industrially at the Megaton scale. They find numerous commercial applications, particularly in catalysis, adsorption, and separation. Under ambient conditions aluminosilicate zeolites are stable when exposed to water or water vapor. However, at extreme conditions as high temperature, high water vapor pressure or increased acidity/basicity, their crystalline framework can be destroyed....

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Section: Discussionmentioning

confidence: 99%

Zeolite (In)Stability under Aqueous or Steaming Conditions

et al. 2020

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“…With electron microscopy, not only crystal structures but also fine details of nanocrystals can be revealed. 6,7 However, there are also limitations for studying nanoporous crystals using EM.…”

Section: Introductionmentioning

confidence: 99%

“…We can change the energy and control its direction and its illumination (parallel or convergent) through the Coulomb force or Lorentz force. With electron microscopy, not only crystal structures but also fine details of nanocrystals can be revealed. , However, there are also limitations for studying nanoporous crystals using EM. For one thing, sample thickness should always be concerned in transmission electron microscopy (TEM).…”

Section: Introductionmentioning

confidence: 99%

Electron Microscopy of Nanoporous Crystals

et al. 2021

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Conspectus Nanoporous crystals, such as silica mesoporous crystals (SMCs), zeolites, metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), usually have unique geometrical features of periodically arranged pores from micro-, meso- to macro-scale. They have great potential to be structurally designed toward novel materials for various applications, such as storage, separation, and catalysis. In addition to the synthesis and applications of these materials, the structural analysis of nanoporous crystals is also critical for obtaining novel materials and unravelling their structure–property relationships. The crystal structure determines the pore size and connectivity of cages/channels, which are closely related to the performance of these materials in adsorption and catalysis. However, there are significant challenges in structural analysis due to small crystal size, electron-beam sensitivity, and local defects. Due to the strong interaction between electrons and matter, electron microscopy (EM) can provide rich structural information, which at the same time can also cause structural damage to samples. As early as 1960s, EM had been used to directly observe the lattice fringes of zeolites. Subsequently, the structures of many nanoporous crystals were solved and structural details such as defects, intergrowths, and surface structures were revealed by exploiting EM during the past decades. With the development of three-dimensional electron diffraction (3D ED) and low-dose high-resolution electron microscopy imaging, these approaches become more routine for solving the structure of nanocrystals and for revealing the local structural details. In this Account, we present our previous work on EM studies of several typical nanoporous materials, including SMCs, zeolites, MOFs, the TiO2@MIL-101 composite, and COFs. Various methods and strategies were developed and applied to different materials based on the characteristics of their structures. For example, 3D electrostatic potential maps of SMCs can be reconstructed by Fourier synthesis of crystal structure factors obtained from high-resolution TEM images, leading to the discovery of many 3D mesostructures. New zeolites/MOFs/COFs structures, which were not previously solved due to their structural complexity and small crystal size, have been determined using 3D ED data from nanosized crystals or using a combination of electron diffraction and high-resolution imaging. In addition, EM methods for determining the handedness of nanocrystals have also been developed and successfully applied to SMCs and STW zeolite based on high-resolution EM imaging or dynamical electron diffraction. Recently, a new strategy involving a combination of 3D ED and cryogenic protocol was proposed to study the structure, dynamics, and the host–guest interactions in a COF material. The direct-space strategy for structure solution, implemented using a genetic algorithm, was also demonstrated to be a successful approach for solving structures from low-resolution 3D ED data. By now, EM h...

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“…Therefore, long-range techniques such as X-ray diffraction and Rietveld analysis do not always give the short-range information needed. In this sense, transmission electron microscopy is the most powerful methodology as it can provide direct visualization of the framework and the guest species at an atomic level together with crystallographic and chemical information. − All of these results have been achieved with thorough control of the electron dose, as zeolites are strongly beam sensitive. Working in the probe mode offers a quick scan, reducing the sample damage.…”

Section: Introductionmentioning

confidence: 99%

Direct Imaging and Location of Pb²⁺ and K⁺ in EMT Framework-Type Zeolite

et al. 2021

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The understanding of the structural framework and metal locations within zeolites are two critical aspects to tune and further exploit their properties as heterogeneous catalysts, advanced optical devices, or as water remediation materials. The development of electron microscopy has made it possible to observe directly the zeolitic framework and the distribution of extra framework cations within the pores at the atomic level. Here, we have studied the EMT framework providing data with an unprecedented spatial resolution, which have allowed the analysis of the FAU domains present in the framework. Additionally, potassium and lead (introduced by aqueous ion exchange), which were nonperiodically distributed in the pores have been located. An alternative image mode, annular bright field, has been used, proving its usefulness to extend the spatial resolution and increase the sensitivity toward light elements such as bridging oxygen. Finally, the combination of atomic imaging (local information) with the three-dimensional electron diffraction tomography analysis (averaged information) determined the lead-EMT crystal symmetry to be P6 3 mc.

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Structure Solution and Defect Analysis of an Extra-Large Pore Zeolite with UTL Topology by Electron Microscopy

Cited by 7 publications

References 37 publications

Zeolite (In)Stability under Aqueous or Steaming Conditions

Zeolite (In)Stability under Aqueous or Steaming Conditions

Electron Microscopy of Nanoporous Crystals

Direct Imaging and Location of Pb²⁺ and K⁺ in EMT Framework-Type Zeolite

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Structure Solution and Defect Analysis of an Extra-Large Pore Zeolite with UTL Topology by Electron Microscopy

Cited by 7 publications

References 37 publications

Zeolite (In)Stability under Aqueous or Steaming Conditions

Zeolite (In)Stability under Aqueous or Steaming Conditions

Electron Microscopy of Nanoporous Crystals

Direct Imaging and Location of Pb2+ and K+ in EMT Framework-Type Zeolite

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Product

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Direct Imaging and Location of Pb²⁺ and K⁺ in EMT Framework-Type Zeolite