title: Facile proton conduction via ordered water molecules in a phosphonate metal-organic framework.
abstract: A new phosphonate metal-organic framework (MOF) with a layered motif but not that of the classical hybrid inorganic-organic solid is presented. Zn(3)(L)(H(2)O)(2)·2H(2)O (L = [1,3,5-benzenetriphosphonate](6-)), henceforth denoted as PCMOF-3, contains a polar interlayer lined with Zn-ligated water molecules and phosphonate oxygen atoms. These groups serve to anchor free water molecules into ordered chains, as observed by X-ray crystallography. The potential for proton conduction via the well-defined interlayer was studied by (2)H solid-state NMR spectroscopy and AC impedance spectroscopy. The proton conductivity in H(2) was measured as 3.5 × 10(-5) S cm(-1) at 25 °C and 98% relative humidity. More interestingly, an Arrhenius plot gave a low activation energy of 0.17 eV for proton transfer, corroborating the solid-state NMR data that showed exchange between all deuterium sites in the D(2)O analogue of PCMOF-3, even at -20 °C.
authors.affiliation: Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Taylor
authors.forename: Roger K
authors.initials: RK
authors.lastname: Mah
authors.forename: Igor L
authors.initials: IL
authors.lastname: Moudrakovski
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Ratcliffe
authors.forename: Ramanathan
authors.initials: R
authors.lastname: Vaidhyanathan
authors.forename: George K H
authors.initials: GK
authors.lastname: Shimizu