title: A layered mixed zirconium phosphate/phosphonate with exposed carboxylic and phosphonic groups: X-ray powder structure and proton conductivity properties.
abstract: A novel mixed zirconium phosphate/phosphonate based on glyphosine, of formula Zr2(PO4)H5(L)2·H2O [L = (O3PCH2)2NCH2COO], was synthesized in mild conditions. The compound has a layered structure that was solved ab initio from laboratory PXRD data. It crystallizes in the monoclinic C2/c space group with the following cell parameters: a = 29.925(3), b = 8.4225(5), c = 9.0985(4) Å, and β = 98.474(6)°. Phosphate groups are placed inside the sheets and connect the zirconium atoms in a tetradentate fashion, while uncoordinated carboxylate and P-OH phosphonate groups are exposed on the layer surface. Due to the presence of these acidic groups, the compound showed remarkable proton conductivity properties, which were studied in a wide range of temperature and relative humidity (RH). The conductivity is strongly dependent on RH and reaches 1 × 10(-3) S cm(-1) at 140 °C and 95% RH. At this RH, the activation energy of conduction is 0.15 eV in the temperature range 80-140 °C. The similarities of this structure with related structures already reported in the literature were also discussed.
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia , Via Elce di Sotto, 8, 06123 Perugia, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Donnadio
authors.forename: Morena
authors.initials: M
authors.lastname: Nocchetti
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Costantino
authors.forename: Marco
authors.initials: M
authors.lastname: Taddei
authors.forename: Mario
authors.initials: M
authors.lastname: Casciola
authors.forename: Fábio
authors.initials: F
authors.lastname: da Silva Lisboa
authors.forename: Riccardo
authors.initials: R
authors.lastname: Vivani
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D063065:Organophosphonates / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D033362:Powder Diffraction; D011522:Protons; D015040:Zirconium / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D063065:Organophosphonates; D009943:Organophosphorus Compounds; D011522:Protons; C027006:zirconium phosphate; C040598:glyphosphine; D015040:Zirconium; D005998:Glycine