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A zeolite family with expanding structural complexity and embedded isoreticular structures
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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Number of Authors: 11
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.

Place, publisher, year, edition, pages
2015. Vol. 524, 74-78 p.
National Category
Chemical Sciences
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:su:diva-120185DOI: 10.1038/nature14575ISI: 000359002300034OAI: oai:DiVA.org:su-120185DiVA: diva2:851368
Available from: 2015-09-04 Created: 2015-09-02 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Structure Determination and Prediction of Zeolites: A Combined Study by Electron Diffraction, Powder X-Ray Diffraction and Database Mining
Open this publication in new window or tab >>Structure Determination and Prediction of Zeolites: A Combined Study by Electron Diffraction, Powder X-Ray Diffraction and Database Mining
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
zeolites, rotation electron diffraction, structure determination, structure prediction, strong reflections approach
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:su:diva-127750 (URN)978-91-7649-384-7 (ISBN)
Public defence
2016-05-03, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
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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

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