Oxygen condensation in ZIF-8 upon ‘gate opening’ structural transition

Abstract

We report a wide Q-range neutron diffraction study on the absorption of oxygen molecules into deuterated ZIF-8 as the system is taken through its gate-opening transition by applying gas pressure at 85 K. The combination of the quantitative nature of the total neutron scattering technique and the modelling performed using the Empirical Potential Structure Refinement (EPSR) technique has allowed us to determine the behaviour of the absorbed fluid upon condensation within the pores with unprecedented detail. The results show that the number of oxygen molecules found inside the central core of the spherical pore of the sodalite cage does not vary as the gate-opening transition is induced. After going through the structural transition, there is a rearrangement of the molecules and the extra molecules entering the structure are instead pushed towards the window apertures in the open structure. These results help to provide a greater insight into the nature of the structural flexibility of ZIF-8 and to understand its gas sorption behaviour.

GRAPHICAL ABSTRACT

KEYWORDS:

• ZIF-8
• gate opening
• molecular modelling
• gas adsorption

Acknowledgements

We gratefully acknowledge the Science and Technology Facilities Council (STFC) for access to neutron beamtime at ISIS (Experiment RB1620414 at NIMROD) and the ISIS Deuteration Facility for providing the deuterated ligand. We would also like to thank G. Stenning for help on the XRD instrument in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source facilities, and J. Taylor, H. Patel, and J. Callison for their help on the material characterisation. We thank the Research Complex at Harwell (RCaH) for providing access to the materials characterisation facilities. The authors thank T. G. A. Youngs for fruitful discussion.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study will be publicly available in the ISIS Data Journal repository at http://doi.org/10.5286/ISIS.E.83556224 from 21 November 2019 [25].

ORCID

Roberto Boada http://orcid.org/0000-0003-4857-8402

Sofia Diaz-Moreno http://orcid.org/0000-0001-7616-6515

Sarah E. Norman http://orcid.org/0000-0003-0867-1784

Daniel T. Bowron http://orcid.org/0000-0002-4557-1929