Liquid intrusion into zeolitic imidazolate framework-7 nanocrystals: exposing the roles of phase transition and gate opening to enable energy absorption applications

Research output: Contribution to journalArticle

Authors

Colleges, School and Institutes

External organisations

  • Tsinghua University
  • University of Oxford

Abstract

Liquid intrusion into zeolitic imidazolate framework 7 (ZIF-7) has been observed for the first time. Among the three typical phases of ZIF-7, we discover that only the guest-free ZIF-7-II structure can be intruded by mechanical pressure, and intriguingly, this pressurized liquid intrusion behavior is detected only in nanocrystals, indicating the crystal size effect. Because of its unique combination of non-outflow property and high intrusion pressure, water intrusion into ZIF-7-II generates a marked energy dissipation capacity of ∼2 J/g despite its limited pore volume. We present several strategies that can be easily implemented to tune its intrusion pressure and energy dissipation and accomplish material reusability. Remarkably, we found that the pore cavities of ZIF-7-II can accommodate water molecules without experiencing any phase transition, which is entirely different from other solvents whose incorporation will trigger a spontaneous conversion into ZIF-7-I. Our pressure-vs-volume data further reveal that the process of water infiltration and retainment is controlled by the gate-opening/closing mechanism, which has enabled us to probe the viscoelasticity of ZIF-7 via cyclic liquid intrusion experiments. This study has deepened our understanding of the time-dependent mechanical properties of ZIFs and shed new light on the structural flexibility central to the novel applications of metal–organic framework materials.

Details

Original languageUndefined/Unknown
Pages (from-to) 41831−41838
Number of pages8
JournalACS Applied Materials & Interfaces
Volume10
Early online date6 Nov 2018
Publication statusPublished - 5 Dec 2018

Keywords

  • zeolitic imidazolate framework, liquid intrusion, hydrophobicity, gate opening, intrusion pressure, phase transition