Amino-based metal-organic frameworks as stable, highly active basic catalysts

Jorge Gascon Sabate*, Ugur Aktay, Maria D. Hernandez-Alonso, Gerard P.M. van Klink, Freek Kapteijn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

489 Scopus citations

Abstract

Metal-organic frameworks (MOFs) with non-coordinated amino groups, i.e. IRMOF-3 and amino-functionalized MIL-53, are stable solid basic catalysts in the Knoevenagel condensation of ethyl cyanoacetate and ethyl acetoacetate with benzaldehyde. IRMOF-3 DEF exhibits activities that are at least as high as the most active solid basic catalysts reported, with a 100% selectivity to the condensation product. For IRMOF-3 samples the catalytic activity correlated with the accessibility of the basic sites. Diffusion limitations could be excluded for this most active catalyst. A new MOF based on the MIL-53 topology and non-coordinated amino groups has been synthesized and characterized. Although active its poor performance in the studied Knoevenagel condensations is attributed to strong adsorption and diffusion limitations in the 1-D pore structure of this framework. The performance of the IRMOF-3 catalysts demonstrates that the basicity of the aniline-like amino group is enhanced when incorporated inside the MOF structure, increasing the p K a of the basic catalyst and more active than aniline as homogeneous catalyst. The IRMOF-3 catalysts are stable under the studied reaction conditions, and could be reused without significant loss in activity. The catalytic performance of IRMOF-3 in various solvents suggests that this open, accessible and well-defined structure behaves more like homogeneous basic catalysts, in contrast to other solid basic catalysts. By means of DRIFTS, the reaction mechanism has been elucidated, showing spectroscopic evidence of benzaldimine intermediates.

Original languageEnglish (US)
Pages (from-to)75-87
Number of pages13
JournalJournal of Catalysis
Volume261
Issue number1
DOIs
StatePublished - Jan 1 2009

Keywords

  • Base-catalyzed reactions
  • Functional organic sites
  • Heterogeneous catalysis
  • IRMOF-3
  • Knoevenagel condensation
  • MIL-53
  • MOF
  • Metal-organic frameworks

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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