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Structure Determination and Prediction of Zeolites: A Combined Study by Electron Diffraction, Powder X-Ray Diffraction and Database Mining
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). (Xiaodong Zou's research group)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Zeolites are crystalline microporous aluminosilicates with well-defined cavities or channels of molecular dimensions. They are widely used for applications such as gas adsorption, gas storage, ion exchange and catalysis. The size of the pore opening allows zeolites to be categorized into small, medium, large and extra-large pore zeolites. A typical zeolite is the small pore silicoaluminophosphate SAPO-34, which is an important catalyst in the MTO (methanol-to-olefin) process. The properties of zeolite catalysts are determined mainly by their structures, and it is therefore important to know the structures of these materials in order to understand their properties and explore new applications.

Single crystal X-ray diffraction has been the main technique used to determine the structures of unknown crystalline materials such as zeolites. This technique, however, can be used only if crystals larger than several micrometres are available. Powder X-ray diffraction (PXRD) is an alternative technique to determine the structures if only small crystals are available. However, peak overlap, poor crystallinity and the presence of impurities hinder the solution of structures from PXRD data. Electron crystallography can overcome these problems. We have developed a new method, which we have called “rotation electron diffraction” (RED), for the automated collection and processing of three-dimensional electron diffraction data. This thesis describes how the RED method has been applied to determine the structures of several zeolites and zeolite-related materials. These include two interlayer expanded silicates (COE-3 and COE-4), a new layered zeolitic fluoroaluminophosphate (EMM-9), a new borosilicate (EMM-26), and an aluminosilicate (ZSM-25). We have developed a new approach based on strong reflections, and used it to determine the structure of ZSM-25, and to predict the structures of a series of complex zeolites in the RHO family. We propose a new structural principle that describes a series of structurally related zeolites known as “embedded isoreticular zeolite structures”, which have expanding unit cells. The thesis also summarizes several common structural features of zeolites in the Database of Zeolite Structures.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University , 2016. , 108 p.
Keyword [en]
zeolites, rotation electron diffraction, structure determination, structure prediction, strong reflections approach
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-127750ISBN: 978-91-7649-384-7 (print)OAI: oai:DiVA.org:su-127750DiVA: diva2:911097
Public defence
2016-05-03, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2016-04-08 Created: 2016-03-10 Last updated: 2017-02-17Bibliographically approved
List of papers
1. Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction
Open this publication in new window or tab >>Ab initio structure determination of interlayer expanded zeolites by single crystal rotation electron diffraction
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2014 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, no 27, 10593-10601 p.Article in journal (Refereed) Published
Abstract [en]

Layered solids often form thin plate-like crystals that are too small to be studied by single-crystal X-ray diffraction. Although powder X-ray diffraction (PXRD) is the conventional method for studying such solids, it has limitations because of peak broadening and peak overlapping. We have recently developed a software-based rotation electron diffraction (RED) method for automated collection and processing of 3D electron diffraction data. Here we demonstrate the ab initio structure determination of two interlayer expanded zeolites, the microporous silicates COE-3 and COE-4 (COE-n stands for International Network of Centers of Excellence-n), from submicron-sized crystals by the RED method. COE-3 and COE-4 are built of ferrierite-type layers pillared by (-O-Si(CH3)(2)-O-) and (-O-Si(OH)(2)-O-) linker groups, respectively. The structures contain 2D intersecting 10-ring channels running parallel to the ferrierite layers. Because both COE-3 and COE-4 are electron-beam sensitive, a combination of RED datasets from 2 to 3 different crystals was needed for the structure solution and subsequent structure refinement. The structures were further refined by Rietveld refinement against the PXRD data. The structure models obtained from RED and PXRD were compared.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-106454 (URN)10.1039/c4dt00458b (DOI)000338117200032 ()
Note

AuthorCount:9;

Available from: 2014-08-05 Created: 2014-08-04 Last updated: 2017-12-05Bibliographically approved
2. Synthesis and Structure Determination of a Layered Zeolitic Fluoroaluminophosphate and its Transformation to a Three-dimensional Zeolite Framework
Open this publication in new window or tab >>Synthesis and Structure Determination of a Layered Zeolitic Fluoroaluminophosphate and its Transformation to a Three-dimensional Zeolite Framework
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-128932 (URN)
Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2016-04-08Bibliographically approved
3. EMM-26: a two-dimensional medium pore borosilicate zeolitewith 10x10 ring channels solved by rotation electron diffraction
Open this publication in new window or tab >>EMM-26: a two-dimensional medium pore borosilicate zeolitewith 10x10 ring channels solved by rotation electron diffraction
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(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-128933 (URN)
Available from: 2016-04-08 Created: 2016-04-08 Last updated: 2016-04-08Bibliographically approved
4. A zeolite family with expanding structural complexity and embedded isoreticular structures
Open this publication in new window or tab >>A zeolite family with expanding structural complexity and embedded isoreticular structures
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2015 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 524, 74-78 p.Article in journal (Refereed) Published
Abstract [en]

The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal-organic frameworks(1-3), but not for the more widely applicable zeolites(4,5), where new materials are usually discovered using exploratory synthesis. Although millions of hypothetical zeolite structures have been proposed(6,7), not enough is known about their synthesis mechanism to allow any given structure to be prepared. Here we present an approach that combines structure solution with structure prediction, and inspires the targeted synthesis of new super-complex zeolites. We used electron diffraction to identify a family of related structures and to discover the structural 'coding' within them. This allowed us to determine the complex, and previously unknown, structure of zeolite ZSM-25 (ref. 8), which has the largest unit-cell volume of all known zeolites (91,554 cubic angstroms) and demonstrates selective CO2 adsorption. By extending our method, we were able to predict other members of a family of increasingly complex, but structurally related, zeolites and to synthesize two more-complex zeolites in the family, PST-20 and PST-25, with much larger cell volumes (166,988 and 275,178 cubic angstroms, respectively) and similar selective adsorption properties. Members of this family have the same symmetry, but an expanding unit cell, and are related by hitherto unrecognized structural principles; we call these family members embedded isoreticular zeolite structures.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-120185 (URN)10.1038/nature14575 (DOI)000359002300034 ()
Available from: 2015-09-04 Created: 2015-09-02 Last updated: 2017-12-04Bibliographically approved
5. Targeted Synthesis of Two Super-Complex Zeolites with Embedded Isoreticular Structures
Open this publication in new window or tab >>Targeted Synthesis of Two Super-Complex Zeolites with Embedded Isoreticular Structures
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2016 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 16, 4928-4932 p.Article in journal (Refereed) Published
Abstract [en]

A novel structural coding approach combining structure solution, prediction, and the targeted synthesis of new zeolites with expanding complexity and embedded isoreticular structures was recently proposed. Using this approach, the structures of two new zeolites in the RHO family, PST-20 and PST-25, were predicted and synthesized. Herein, by extending this approach, the next two higher generation members of this family, PST-26 and PST-28, have been predicted and synthesized. These two zeolites have much larger unit cell volumes (422 655 Å3 and 614 912 Å3, respectively) than those of the lower generations. Their crystallization was confirmed by a combination of both powder X-ray and electron diffraction techniques. Aluminate and water concentrations in the synthetic mixture were found to be the two most critical factors influencing the structural expansion of embedded isoreticular zeolites under the synthetic conditions studied herein.

National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-127752 (URN)10.1002/anie.201510726 (DOI)
Available from: 2016-03-10 Created: 2016-03-10 Last updated: 2017-11-30Bibliographically approved
6. On the relationship between unit cells and channel systems in high silica zeolites with the butterfly projection
Open this publication in new window or tab >>On the relationship between unit cells and channel systems in high silica zeolites with the butterfly projection
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2015 (English)In: Zeitschrift für Kristallographie - Crystalline Materials, ISSN 2194-4946, Vol. 230, no 5, 301-309 p.Article in journal (Refereed) Published
Abstract [en]

Zeolites are crystalline aluminosilicate framework materials with corner sharing TO 4 (T = Al, Si) tetrahedra forming well-defined pores and channels. Many zeolites are built from similar building units (i.e., isolated units, chains or layers), which are connected in different ways to form a variety of topologies. We have identified ten zeolite frameworks that share the same two-dimensional butterfly net containing 5-, 6- and 10-rings: (MRE)-M-star, FER, MEL, SZR, MFS, MFI, TUN, IMF, BOG and TON. Different orientations of the TO4 tetrahedra within the layer lead to different connectivities between neighboring layers. Some layers are corrugated and some are flat, resulting in different channel systems parallel to the layer. We found some interesting relationships between the unit cell parameters and this channel system that allow the size of the channels and their directions to be deduced from the unit cell dimensions. This may facilitate the prediction of new members of this zeolite family. In addition, other zeolites containing the butterfly layers are also discussed.

Keyword
structure prediction, structure relationship, structure solution, zeolites
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-117715 (URN)10.1515/zkri-2014-1821 (DOI)000353815900003 ()
Available from: 2015-06-12 Created: 2015-06-01 Last updated: 2016-04-08Bibliographically approved

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