A layered mixed zirconium phosphate/phosphonate with exposed carboxylic and phosphonic groups: X-ray powder structure and proton conductivity properties

Inorg Chem. 2014 Dec 15;53(24):13220-6. doi: 10.1021/ic502473w. Epub 2014 Nov 26.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carboxylic Acids / chemistry*
  • Crystallography, X-Ray
  • Glycine / analogs & derivatives*
  • Glycine / chemistry
  • Models, Molecular
  • Organophosphonates / chemistry*
  • Organophosphorus Compounds / chemistry*
  • Powder Diffraction
  • Protons
  • Zirconium / chemistry*

Substances

  • Carboxylic Acids
  • Organophosphonates
  • Organophosphorus Compounds
  • Protons
  • zirconium phosphate
  • glyphosphine
  • Zirconium
  • Glycine