Zr6O8 node-catalyzed butene hydrogenation and isomerization in the metal−organic framework NU-1000

Kenton E. Hicks, Andrew S. Rosen, Zoha H. Syed, Randall Q. Snurr, Omar K. Farha, Justin M. Notestein

Research output: Contribution to journalArticlepeer-review

Abstract

Zirconium-based metal−organic frameworks (Zr-MOFs) have been increasingly studied over the past two decades as heterogeneous catalysts due to their synthetic tunability, well-defined nature, and chemical stability. In contrast to traditional zirconia-based heterogeneous catalysts, the community has assumed that Zr-MOFs are inert catalyst supports that do not participate directly in hydrocarbon transformations, such as olefin hydrogenation and isomerization. Here, we report that the Zr-MOF NU-1000 is capable of catalyzing olefin hydrogenation and isomerization, without any postsynthetic modifications, under a hydrogen atmosphere. We probe H2 activation over the nodes of NU-1000 via spectroscopic and computational techniques revealing that H2 dissociation can occur heterolytically across coordinatively unsaturated Zr sites and proximal hydroxide and μ3-oxo ligands. These results, along with catalytic experiments, suggest that H2 activation results in node-supported zirconium hydrides capable of the hydrogenation and isomerization of 1-butene. When examining rate dependence on the partial pressure of H2, we observe first-order dependence for hydrogenation and half-order dependence for isomerization. Half-order H2 rate dependence is consistent with a mechanism where both fragments of cleaved H2 are active for 1-butene isomerization, suggesting that heterolytic cleavage generates acidic protons resulting in parallel, acid-, and hydride-catalyzed isomerization pathways. This work shows that Zr-MOFs have more diverse reactivity than the current literature may suggest and opens possibilities for ways in which Zr-MOFs can be used as heterogeneous catalysts and supports.

Original languageEnglish
Pages (from-to)14959-14970
Number of pages12
JournalACS Catalysis
Volume10
Issue number24
DOIs
Publication statusPublished - Dec 18 2020

Keywords

  • Heterogeneous catalysis
  • Hydrogen dissociation
  • Metal−organic framework
  • Olefin hydrogenation
  • Olefin isomerization
  • Zirconium

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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