Study elucidates mechanism of MOF-mediated catalysis | March 19, 2018 Issue - Vol. 96 Issue 12 | Chemical & Engineering News
Volume 96 Issue 12 | p. 8 | Concentrates
Issue Date: March 19, 2018

Study elucidates mechanism of MOF-mediated catalysis

Findings could lead to custom-designed catalysts with improved activity and selectivity
Department: Science & Technology
Keywords: Metal-organic frameworks, MOF, catalysis, catalyst
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This zirconium-based MOF cluster (shown here in simplified form) selectively converts ethanol to diethyl ether due to catalytically active defects.
Credit: J. Am. Chem. Soc.
This image shows the structure of a catalytic zirconium-based cluster in a MOF and a reaction occurring on its surface.
 
This zirconium-based MOF cluster (shown here in simplified form) selectively converts ethanol to diethyl ether due to catalytically active defects.
Credit: J. Am. Chem. Soc.

In addition to garnering widespread attention as materials for gas storage and separation, metal-organic frameworks (MOFs) have shown themselves to be worthy catalysts in a limited number of reactions. MOFs’ catalytic usefulness could be boosted by design, if researchers understood how these crystalline porous materials drive reactions. But many details remain unknown. So a team led by Christopher J. Cramer and Laura Gagliardi of the University of Minnesota, Twin Cities, and Bruce C. Gates of the University of California, Davis, coupled spectroscopy and computational methods to ferret out mechanistic details of a test reaction—ethanol dehydration on the MOFs UiO-66 and UiO-67 (J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.7b13330). These MOFs contain Zr6O8 clusters joined by dicarboxylic acid linkers. Because MOF clusters function as catalysts when they have defects—for example, vacancies due to missing linkers—the researchers deliberately introduced vacancies synthetically. Analysis of the resulting MOFs shows that they dehydrate ethanol selectively, forming diethyl ether, not ethylene, the competing product. The team notes that the key to selectivity is having adjacent vacancies, which enables ethanol molecules to bind to neighboring sites on the clusters and facilitates ether formation via an SN2 mechanism.


CORRECTION: This story was updated March 20, 2018, to correct Bruce C. Gates’s affiliation. He is a professor at the University of California, Davis, not the University of California, Irvine.

 
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