Mobility of Aromatic Guests and Isobutane in ZIF-8 Metal-Organic Framework Studied by 2H Solid State NMR Spectroscopy

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10 Citations (Scopus)

Abstract

Metal-organic framework ZIF-8 is renowned for its adsorption and separation properties influenced by the framework flexibility. Although much effort was put into understanding the molecular mechanism of such gate-opening (dynamical and static), the mobility of large guest themselves remained unclear. In this work, we present a detailed 2H solid-state NMR investigation of large guests (xylene isomers, benzene, toluene, and isobutane) confined inside the ZIF-8. Evolution of line shape and T1, T2 relaxation times with temperature were interpreted in terms of existence of three different motional states for diffusing guest molecules: (i) the highly mobile guest molecules located in the central part of the cage; (ii) the bound state for a guest located on the cage wall or near the window; and (iii) the guest squeezing through the window with a subsequent release to the next cage. We report detailed quantitative analysis of molecular dynamics in each of the states and the kinetics of exchange between the bound and mobile states.

Original languageEnglish
Pages (from-to)13765-13774
Number of pages10
JournalJournal of Physical Chemistry C
Volume123
Issue number22
DOIs
Publication statusPublished - 6 Jun 2019

Keywords

  • ZEOLITIC IMIDAZOLATE FRAMEWORKS
  • DEUTERIUM NMR
  • SEPARATION
  • ADSORPTION
  • CO2
  • DIFFUSION
  • MIXTURES
  • DYNAMICS
  • TEMPERATURE
  • ADSORBENTS

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