title: Water-mediated proton conduction in a robust triazolyl phosphonate metal-organic framework with hydrophilic nanochannels.
abstract: The development of water-mediated proton-conducting materials operating above 100 °C remains challenging because the extended structures of existing materials usually deteriorate at high temperatures. A new triazolyl phosphonate metal-organic framework (MOF) [La3L4(H2O)6]Cl⋅x H2O (1, L(2-) = 4-(4H-1,2,4-triazol-4-yl)phenyl phosphonate) with highly hydrophilic 1D channels was synthesized hydrothermally. Compound 1 is an example of a phosphonate MOF with large regular pores with 1.9 nm in diameter. It forms a water-stable, porous structure that can be reversibly hydrated and dehydrated. The proton-conducting properties of 1 were investigated by impedance spectroscopy. Magic-angle spinning (MAS) and pulse field gradient (PFG) NMR spectroscopies confirm the dynamic nature of the incorporated water molecules. The diffusivities, determined by PFG NMR and IR microscopy, were found to be close to that of liquid water. This porous framework accomplishes the challenges of water stability and proton conduction even at 110 °C. The conductivity in 1 is proposed to occur by the vehicle mechanism.
authors.affiliation: Fakultät für Chemie und Mineralogie, Universität Leipzig, Johannisallee 29, 04103 Leipzig (Germany).
authors.forename: Salma
authors.initials: S
authors.lastname: Begum
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Wang
authors.forename: Anna
authors.initials: A
authors.lastname: Donnadio
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Costantino
authors.forename: Mario
authors.initials: M
authors.lastname: Casciola
authors.forename: Rustem
authors.initials: R
authors.lastname: Valiullin
authors.forename: Christian
authors.initials: C
authors.lastname: Chmelik
authors.forename: Marko
authors.initials: M
authors.lastname: Bertmer
authors.forename: Jörg
authors.initials: J
authors.lastname: Kärger
authors.forename: Jürgen
authors.initials: J
authors.lastname: Haase
authors.forename: Harald
authors.initials: H
authors.lastname: Krautscheid
keywords: diffusion studies; impedance spectroscopy; metal-organic frameworks; microporous materials; proton conduction