Proton Conduction Inhibited by Xe Hydrates in the Water Nanotube of the Molecular Porous Crystal {{[RuIII(H2bim)3](TMA)}2· mH2O}n

Hiroshi Matsui, Tomotaka Sasaki, Makoto Tadokoro

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1 Citation (Scopus)

Abstract

Gas sorption and molecular (ionic) storages are important functionalities in porous materials. In molecular porous crystal {{[RuIII(H2bim)3](TMA)}2·mH2O}n, the hydrophilic nanochannel accommodates the water nanotube (WNT) composed of a 4461074-polyhedral cage. The experiment on weight change reveals that the cage structure is maintained above 50% RH (relative humidity) at 294 K. As the relative humidity is reduced from 80 to 50% RH, the proton conductivity exponentially decreases from 0.02 to 0.01 (ω cm)-1 owing to the dehydration of inner H2O molecules through WNT, which acts as a nanofluidic channel. Upon pressurizing Xe at 0.4 MPa for 50% RH, the proton conductivity exponentially decreases and approaches 0 (ω cm)-1. The infrared and 129Xe-NMR experiments make clear that Xe together with about 25H2O molecules per cage are stabilized in WNT at low pressures compared to Xe-clathrate hydrate. Those results experimentally demonstrate that the Xe hydrate inhibits the proton conduction. The formation of Xe hydrate is characterized by fast and slow processes with a translational diffusion constant of 1 × 10-10 and 6 × 10-12 m2/s, respectively. The reorganization and hardening of the hydrogen-bonding water network are considered to diminish the conducting pass of proton, and to reduce the protonic transfer from H3O+ to adjacent H2O.

Original languageEnglish
Pages (from-to)20413-20419
Number of pages7
JournalJournal of Physical Chemistry C
Volume123
Issue number33
DOIs
Publication statusPublished - 2019 Aug 22

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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