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.

Boosting Proton Conductivity in Highly Robust 3D Inorganic Cationic Extended Frameworks through Ion Exchange with Dihydrogen Phosphate Anions

“…The smaller p K a value of H 2 PO 4 − (7.2) than H 2 BO 3 − (12.74) results in more than one order of magnitude higher conductivity for NDTBP than NDTB. Such high proton conductivities of CEFs, especially for NDTBP, are comparable to the most efficient MOF counterparts, such as PCMOF‐3 (3.5×10 −5 S cm −1 at 25 °C and 98 % RH),11d ZPGly (1×10 −3 S cm −1 at 140 °C and 95 % RH),18 Ca‐PiPhtA‐NH 3 (6.6×10 −3 S cm −1 at 24 °C and 98 % RH),19 PCMOF2 1/2 (2.1×10 −2 S cm −1 at 85 °C and 90 % RH) ,[11b] PCMOF10 (3.55×10 −2 S cm −1 at 70 °C and 95 % RH),13 CPM‐103a (5.8×10 −2 S cm −1 at 22.5 °C and 98 % RH),14 and UiO‐66(SO 3 H) 2 (8.4×10 −2 S cm −1 at 80 °C and 90 % RH) 12…”

“…Eur.J.2015, 21,17591 -17595 www.chemeurj.org stitutiono fp roton-rich H 2 PO 4 À for Cl À .T he smaller pK a value of H 2 PO 4 À (7.2) than H 2 BO 3 À (12.74) results in more than one order of magnitude higher conductivity for NDTBP than NDTB. Such high proton conductivities of CEFs, especiallyf or NDTBP, are comparablet ot he most efficient MOF counterparts, such as PCMOF-3 (3.5 10 À5 Scm À1 at 25 8Ca nd 98 %R H), [11d] ZPGly (1 10 À3 Scm À1 at 140 8Ca nd 95 %R H), [18] Ca-PiPhtA-NH 3 (6.6 10 À3 Scm À1 at 24 8Ca nd 98 %R H), [19] PCMOF2 1/2 (2.1 10 À2 Scm À1 at 85 8Ca nd 90 %R H) ,[11b] PCMOF10 (3.55 10 À2 Scm À1 at 70 8Ca nd 95 %R H), [13] CPM-103a (5.8 10 À2 Scm À1 at 22.5 8Ca nd 98 %R H), [14] and UiO-66(SO 3 H) 2 (8.4 10 À2 Scm À1 at 80 8Cand 90 %R H). [12] In addition, the proton conductivitieso fY bO(OH)P and NDTBP are highly humidity and temperature-dependent.…”

Immobilized Palladium Nanoparticles on Zirconium Carboxy-Aminophosphonates Nanosheets as an Efficient Recoverable Heterogeneous Catalyst for Suzuki–Miyaura and Heck Coupling

“…Recently, in our research group, a layered zirconium phosphate-phosphonate with the formula Zr 2 (PO 4 )[(O 3 PCH 2 ) 2 NHCH 2 COOH] 2 ·H 2 O (ZPGly) was obtained by the reaction among Zr(IV), phosphoric acid and N,N-bis(phosphonomethyl)glycine [35]. For the reader's convenience, a brief description of ZPGly is reported.…”

“…In this study, we used a layered zirconium phosphate glycine diphosphonate [35] because of its peculiarity that revealed it to be suitable for our tasks. This compound possesses a large number of carboxylic, phosphonic and amino groups on the surface of layers that are not coordinated to structural metal atoms and therefore are available for the coordination of Pd.…”

Layered Tb‐Doped Yttrium Carboxyphosphonate Nanocrystals as Efficient Filler for PEDOT:PSS Composite Films

“…[11] Several divalent or trivalent metal phosphonocarboxylate with different structures and dimensionalities, also containinga uxiliary ligands, have been recently reported in literature. [12][13][14][15] Among them, N-(phosphonomethyl)glycine (glyphosate) and its related diphosphonica nalogous (glyphosine) are simple and cheap buildingb locks already used for the synthesis of layered bivalent( Mg, Ca and Ba) [15,16] trivalent (Gd and Eu) [17,18] and tetravalent( Zr) phosphonates used as fillers for polymeric composites, [19] in proton conductivity, [20] as MRI contrast agents [17] and in heterogeneous catalysis. Ac ommon feature of all these compounds is the presence of free carboxylic groups exposed on the layer surfacet hat make them strongly hydrophilic and able to interactw ith polar exfoliating agentsl ike alkylamines.…”