Design strategies for the molecular level synthesis of supported catalysts

Staci L. Wegener, Tobin J Marks, Peter C Stair

Research output: Contribution to journalArticle

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Abstract

S upported catalysts, metal or oxide catalytic centers constructed on an underlying solid phase, are making an increasingly important contribution to heterogeneous catalysis. For example, in industry, supported catalysts are employed in selective oxidation, selective reduction, and polymerization reactions. Supported structures increase the thermal stability, dispersion, and surface area of the catalyst relative to the neat catalytic material. However, structural and mechanistic characterization of these catalysts presents a formidable challenge because traditional preparations typically afford complex mixtures of structures whose individual components cannot be isolated. As a result, the characterization of supported catalysts requires a combination of advanced spectroscopies for their characterization, unlike homogeneous catalysts, which have relatively uniform structures and can often be characterized using standard methods. Moreover, these advanced spectroscopic techniques only provide ensemble averages and therefore do not isolate the catalytic function of individual components within the mixture. New synthetic approaches are required to more controllably tailor supported catalyst structures. In this Account, we review advances in supported catalyst synthesis and characterization developed in our laboratories at Northwestern University. We first present an overview of traditional synthetic methods with a focus on supported vanadium oxide catalysts. We next describe approaches for the design and synthesis of supported polymerization and hydrogenation catalysts, using anchoring techniques which provide molecular catalyst structures with exceptional activity and high percentages of catalytically significant sites. We then highlight similar approaches for preparing supported metal oxide catalysts using atomic layer deposition and organometallic grafting. Throughout this Account, we describe the use of incisive spectroscopic techniques, including high-resolution solid state NMR, UV-visible diffuse reflectance (DRS), UV-Raman, and X-ray absorption spectroscopies to characterize supported catalysts. We demonstrate that it is possible to tailor and isolate defined surface species using a molecularly oriented approach. We anticipate that advances in catalyst design and synthesis will lead to a better understanding of catalyst structure and function and, thus, to advances in existing catalytic processes and the development of new technologies.

Original languageEnglish
Pages (from-to)206-214
Number of pages9
JournalAccounts of Chemical Research
Volume45
Issue number2
DOIs
Publication statusPublished - 2012

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Catalyst supports
Catalysts
Oxides
Metals
Polymerization
Vanadium
X ray absorption spectroscopy
Atomic layer deposition
Organometallics
Complex Mixtures
Catalysis
Hydrogenation
Thermodynamic stability
Nuclear magnetic resonance
Spectroscopy
Oxidation

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Design strategies for the molecular level synthesis of supported catalysts. / Wegener, Staci L.; Marks, Tobin J; Stair, Peter C.

In: Accounts of Chemical Research, Vol. 45, No. 2, 2012, p. 206-214.

Research output: Contribution to journalArticle

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