Building MOF bottles around phosphotungstic acid ships: One-pot synthesis of bi-functional polyoxometalate-MIL-101 catalysts

Jana Juan-Alcañiz, Enrique V. Ramos-Fernandez, Ugo Lafont, Jorge Gascon Sabate*, Freek Kapteijn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

276 Scopus citations

Abstract

A new strategy has been developed for the direct encapsulation of polyoxometalates (POMs) into MIL-101(Cr). The addition of phosphotungstic acid (PTA) to the synthesis mixture of MIL-101 yields the direct encapsulation of chromium-containing polyoxometalates (POMs) inside the MOF structure, with a good distribution over the MIL-101 crystals. Vibrational Spectroscopy (DRIFT, Raman, UV-Vis) reveals the partial substitution of tungsten by Cr3+ resulting in the so-called lacunary structures, which are highly active in catalysis. The medium-sized cavities of MIL-101 are occupied by POM units bigger than their pentagonal windows when this one-pot approach is followed, and no leaching is observed. These new catalysts show the highest activities reported to date at 313 K for the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate when using apolar toluene as solvent as well as when using polar DMF and ethanol, with TOFs exceeding 600 h-1. In addition, they exhibit a remarkable activity in two acid-catalyzed reactions, the esterification of n-butanol with acetic acid in liquid phase slurry operation and the dimethyl ether production from methanol in a fixed bed gas phase operation, in contrast to the poor or absent activity of the catalysts prepared via the impregnation of the polyoxometalate in MIL-101, where the strong interaction between POM and support deteriorates the catalytic performance.

Original languageEnglish (US)
Pages (from-to)229-241
Number of pages13
JournalJournal of Catalysis
Volume269
Issue number1
DOIs
StatePublished - Jan 1 2010

Keywords

  • Bi-functional catalyst
  • Encapsulated catalyst
  • Esterification
  • Etherification
  • Knoevenagel condensation
  • MIL-101
  • Metal organic frameworks
  • Phosphotungstic acid
  • Polyoxometalates

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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