Flexible pores of a metal oxide-based capsule permit entry of comparatively larger organic guests

Ayala Ziv, Alina Grego, Sivil Kopilevich, Leila Zeiri, Pere Miro, Carles Bo, Achim Müller, Ira A. Weinstock

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


In zeolites and other rigid solid-state oxides, substrates whose sizes exceed the pore dimensions of the material are rigorously excluded. Now, using a porous 3 nm diameter capsule-like oxomolybdate complex [{MoVI 6O21(H2O)6}12{(MoV 2O4)30(OAc)21(H2O) 18}]33- as a water-soluble analogue of solid-state oxides (e.g., as a soluble analogue of 3 Å molecular sieves), we show that carboxylates (RCO2-) can negotiate passage through flexible Mo 9O9 pores in the surface of the capsule and that the rates follow the general trend R = 1° 2° > 3° phenyl (no reaction). Surprisingly, the branched alkanes (R = iso-Pr and tert-Bu) enter the capsule even though they are larger than the crystallographic dimensions of the Mo 9O9 pores. Four independent lines of spectroscopic and kinetic evidence demonstrate that these organic guests enter the interior of the capsule through its Mo9O9 apertures and that no irreversible changes in the metal oxide framework are involved. This unexpected phenomenon likely reflects the greater flexibility of molecular versus solid-state structures and represents a sharp departure from traditional models for diffusion through porous solid-state (rigid) oxides.

Original languageEnglish
Pages (from-to)6380-6382
Number of pages3
JournalJournal of the American Chemical Society
Issue number18
StatePublished - 13 May 2009

ASJC Scopus subject areas

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


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