An Exceptionally Stable Metal-Organic Framework Supported Molybdenum(VI) Oxide Catalyst for Cyclohexene Epoxidation

Hyunho Noh, Yuexing Cui, Aaron W. Peters, Dale R. Pahls, Manuel A. Ortuno, Nicolaas A. Vermeulen, Christopher J. Cramer, Laura Gagliardi, Joseph T Hupp, Omar K. Farha

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Abstract

Molybdenum(VI) oxide was deposited on the Zr6 node of the mesoporous metal-organic framework NU-1000 via condensed-phase deposition where the MOF is simply submerged in the precursor solution, a process named solvothermal deposition in MOFs (SIM). Exposure to oxygen leads to a monodisperse, porous heterogeneous catalyst, named Mo-SIM, and its structure on the node was elucidated both computationally and spectroscopically. The catalytic activity of Mo-SIM was tested for the epoxidation of cyclohexene. Near-quantitative yields of cyclohexene oxide and the ring-opened 1,2-cyclohexanediol were observed, indicating activity significantly higher than that of molybdenum(VI) oxide powder and comparable to that of a zirconia-supported analogue (Mo-ZrO2) prepared in a similar fashion. Despite the well-known leaching problem of supported molybdenum catalysts (i.e., loss of Mo species thus causes deactivation), Mo-SIM demonstrated no loss in the metal loading before and after catalysis, and no molybdenum was detected in the reaction mixture. In contrast, Mo-ZrO2 led to significant leaching and close to 80 wt % loss of the active species. The stability of Mo-SIM was further confirmed computationally, with density functional theory calculations indicating that the dissociation of the molybdenum(VI) species from the node of NU-1000 is endergonic, corroborating the experimental data for the Mo-SIM material.

Original languageEnglish
Pages (from-to)14720-14726
Number of pages7
JournalJournal of the American Chemical Society
Volume138
Issue number44
DOIs
Publication statusPublished - Nov 9 2016

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Noh, H., Cui, Y., Peters, A. W., Pahls, D. R., Ortuno, M. A., Vermeulen, N. A., Cramer, C. J., Gagliardi, L., Hupp, J. T., & Farha, O. K. (2016). An Exceptionally Stable Metal-Organic Framework Supported Molybdenum(VI) Oxide Catalyst for Cyclohexene Epoxidation. Journal of the American Chemical Society, 138(44), 14720-14726. https://doi.org/10.1021/jacs.6b08898