2026-05-30T05:39:47Zhttps://riuma.uma.es/rest/oai/request

oai:riuma.uma.es:10630/210422026-02-03T10:50:49Zcom_10630_2254col_10630_37953

Guest Molecule-Responsive Functional Calcium Phosphonate Frameworks for Tuned Proton Conductivity Bazaga-García, Montse Pérez-Colodrero, Rosario Mercedes Papadaki, M. Garczarek, Piotr Zon, Jerzy Olivera-Pastor, Pascual Losilla, Enrique R. León-Reina, Laura García-Aranda, Miguel Ángel Choquesillo-Lazarte, Duane Demadis, Konstantinos D. Cabeza-Díaz, Aurelio Química We report the synthesis, structural characterization, and functionality of an open-framework hybrid that combines Ca2+ ions and the rigid polyfunctional ligand 5-(dihydroxyphosphoryl) isophthalic acid (PiPhtA). Ca-PiPhtA-I is obtained by slow crystallization at ambient conditions from acidic (pH≈3) aqueous solutions. It possesses a high water content (both Ca coordinated and in the lattice), and importantly, it exhibits water-filled 1D channels. At 75 °C, Ca-PiPhtA-I is partially dehydrated and exhibits a crystalline diffraction pattern that can be indexed in a monoclinic cell with parameters close to the pristine phase. Rietveld refinement was carried out for the sample heated at 75 °C, Ca-PiPhtA-II, using synchrotron powder X-ray diffraction data.All connectivity modes of the “parent” Ca-PiPhtA-I framework are retained in Ca-PiPhtA-II. Upon Ca-PiPhtA-I exposure to ammonia vapors (28% aqueous NH3) a new derivative is obtained (Ca-PiPhtA-NH3) containing 7 NH3 and 16 H2O molecules according to elemental and thermal analyses. Ca-PiPhtA-NH3 exhibits a complex X-ray diffraction pattern with peaks at 15.3 and 13.0 Å that suggest partial breaking and transformation of the parent pillared structure. Although detailed structural identification of Ca-PiPhtA-NH3 was not possible, due in part to nonequilibrium adsorption conditions and the lack of crystallinity, FT-IR spectra and DTA-TG analysis indicate profound structural changes compared to the pristine Ca-PiPhtA-I. At 98% RH and T = 24 °C, proton conductivity, σ, for Ca PiPhtA-I is 5.7 ×10−4 S·cm−1. It increases to 1.3 × 10−3 S·cm−1 upon activation by preheating the sample at 40 °C for 2 h followed by water equilibration at room temperature under controlled conditions. Ca-PiPhtA-NH3 exhibits the highest proton conductivity, 6.6 × 10−3 S·cm−1, measured at 98% RH and T = 24 °C. Ea for proton transfer in the above-mentioned frameworks range between 0.23 and 0.4 eV, typical of a Grothuss mechanism of proton conduction. 2021-03-08T08:48:15Z 2021-03-08T08:48:15Z 2021-03-08T08:48:15Z 2014-03-18 journal article J. Am. Chem. Soc. 2014, 136, 5731−5739 https://hdl.handle.net/10630/21042 dx.doi.org/10.1021/ja500356z eng open access American Chemical Society