Formation of Layered Proton-Conducting Zirconium and Titanium Organophosphonates by Topotactic Reaction: Physicochemical Properties, Proton Dynamics, and Atomic-Resolution Structure

Immobilization of Alendronate on Zirconium Phosphate Nanoplatelets

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.

Ionothermal synthesis of a highly crystalline zirconium phosphate proton conductor

A highly crystalline one-dimensional zirconium phosphate, (NH₄)₂[ZrF(PO₄)(HPO₄)] (ZrP-3), was facilely synthesized by the ionothermal method. The robust structure and rich hydrogen-bonded network make ZrP-3 an excellent proton conductor by having a proton conductivity higher than 10^-2 S cm^-1 at 90 °C and 95% RH. The remarkable stability makes ZrP-3 a promising solid electrolyte material for proton exchange membrane fuel cells.

Colossal Dielectric Responses from the Wide Band Gap 2D-Semiconducting Amine Templated Hybrid Framework Materials

Two unprecedented organic amine templated silver organophosphonate hybrid solids have been synthesized hydrothermally by varying the molar ratio of the reactants. Both of the compounds consist of novel tetra- and penta-nuclear silver phosphonate basic building units. The dielectric constants are extremely large due to the charge separation of anionic metal phosphonate frameworks and cationic templated piperazine moieties in the compounds, as found for the first time in a hybrid organophosphate family. The conductivity and UV-visible absorption studies provide strong evidence about the semiconducting nature of the present compounds.

Proton conductive Zr-based MOFs

The preparation strategies, structures, proton conductivity, conducting mechanism, application prospects and future research trends of zirconium-based MOFs are reviewed and highlighted.