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Updated: Jun 19, 2026

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Dynamic structural changes in a molecular zeolite-supported iridium catalyst for ethene hydrogenation
1Department of Chemical Engineering and Materials Science, University of California, Davis One Shields Avenue, Davis, California 95616, USA.
Catalyst structure dynamically changes during reactions. Researchers used X-ray absorption to show iridium clusters reversibly forming and breaking apart within zeolite Y cages, controlled by reactant gas ratios.
Area of Science:
- Catalysis
- Materials Science
- Surface Chemistry
Background:
- Catalyst structure is dynamic and sensitive to the operating environment.
- Real-time characterization of these structural changes at the molecular level is crucial for understanding catalyst performance.
Purpose of the Study:
- To investigate the real-time molecular-level structural changes of a working supported catalyst.
- To demonstrate the ability to tune catalyst structure by controlling the reactive environment.
Main Methods:
- Time-resolved extended X-ray absorption fine structure (EXAFS) spectroscopy.
- Infrared (IR) spectroscopy using carbon monoxide (CO) as a probe.
Main Results:
- Demonstrated reversible interconversion between mononuclear iridium complexes and tetrairidium clusters within zeolite Y cages.
- Showed that the iridium structure is controlled by the ethene/hydrogen (C(2)H(4)/H(2)) ratio during ethene hydrogenation.
- Observed cluster break-up in ethene-rich feed and cluster reformation in hydrogen-rich feed, confirmed by changes in Ir-Ir coordination number and IR spectra.
Conclusions:
- The study provides the first evidence of tuning solid catalyst structure at the molecular scale through reactant composition control.
- This molecular-level control over catalyst structure offers new avenues for catalyst design and optimization.
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