The Dependence of Olefin Hydrogenation and Isomerization Rates on Zirconium Metal-Organic Framework Structure

Kenton E. Hicks, Andrew T.Y. Wolek, Omar K. Farha*, Justin M. Notestein

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Zirconium metal-organic frameworks (Zr-MOFs) are a structurally diverse and well-defined class of materials studied in heterogeneous catalysis. Previously, we showed that partial dehydration of the Zr6O8node in NU-1000 results in heterolytic H2cleavage over adjacent Lewis acid and base sites, leading to catalytic conversion of 1-butene. In this work, given the ubiquity of the Zr6O8node as a secondary building unit (SBU) in Zr-MOFs, with many different potential MOF topologies and capping ligands surrounding the cluster, we study the influence of thermal pretreatments and MOF topology (MOF-808, NU-1000, UiO-66, and NU-1000-NDC) on the activity of the Zr6O8cluster for H2activation and 1-butene hydrogenation and isomerization. Diffuse reflectance IR in the presence of H2and pyridine shows that both thermal pretreatment and MOF topology affect the Brønsted acidity of protons generated from H2activation and their resulting activity for olefin conversion. High isomerization activity of dehydrated NU-1000 is correlated with the formation of μ3OH species after H2activation. Additionally, catalytic studies show that the geometry of open coordination sites on individual Zr6O8nodes influences butene hydrogenation. For this reason, MOF-808 gives anomalously low hydrogenation activity, despite its relatively high total number of open coordination sites, as calculated either from its crystal structure or from NH3adsorption. These results reiterate the importance of pretreatment in defining MOF catalytic activity and demonstrate that MOF topology, outside of simply affecting node accessibility, influences reactivity at individual nodes.

Original languageEnglish (US)
Pages (from-to)13671-13680
Number of pages10
JournalACS Catalysis
Volume12
Issue number21
DOIs
StatePublished - Nov 4 2022

Keywords

  • heterogeneous catalysis
  • hydrogen activation
  • metal-organic framework
  • olefin hydrogenation
  • olefin isomerization
  • topology
  • zirconium

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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