Adsorption of n-alkanes in ZIF-8: Influence of crystal size and framework dynamics

Andrzej Sławek, Kornel Roztocki, Dorota Majda, Sonia Jaskaniec, Thijs J.H. Vlugt, Wacław Makowski

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Due to its exceptional chemical and thermal stability, ZIF-8 is one of the most promising representatives of nanoporous metal-organic frameworks. In this work, we investigate adsorption properties of this material both experimentally and theoretically. The experiments were carried out on 8 preparations differing in morphology of the crystals. Adsorption was studied in isothermal approach exploiting standard adsorbates, such as N2 or CO2, as well as in isobaric regime with C5–C9 linear alkanes. The latter were performed with the novel quasi-equilibrated temperature-programmed desorption and adsorption (QE-TPDA) technique showing that a complexity of n-alkanes adsorption mechanism in ZIF-8 depends on the nature of adsorbate. Unexpectedly, for adsorption of C7–C9 n-alkanes a two-step process was found. QE-TPDA yielded high quality adsorption isobars which were successfully reproduced by Grand-Canonical Monte Carlo molecular simulations. The calculations showed that the specific adsorption behaviour of ZIF-8 is due to the fact that its structure undergoes conformational changes in order to adapt to the guest molecules. QE-TPDA measurements with n-nonane were performed at conditions close to saturation of the adsorbate. This allowed to observe surface-related adsorption on the ZIF-8 crystals, which was correlated with their size.

Original languageEnglish
Article number110730
Number of pages9
JournalMicroporous and Mesoporous Materials
Volume312
DOIs
Publication statusPublished - 2021

Keywords

  • Adsorption
  • Monte Carlo
  • n-Alkanes
  • Quasi-equilibrated thermodesorption
  • ZIF-8

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