Metalo Hydrogen-Bonded\nOrganic Frameworks Constructed\nby Coordinated Chains for Magnetic and Proton-Conductive Bifunctionality

Metalo hydrogen-bonded organic frameworks (MHOFs) have\nreceived\ngrowing interest in designing crystalline functional materials. However,\nreports on bifunctional MHOFs showing magnetic and proton-conductive\nproperties are extremely limited and their design is challenging.\nHerein, we investigated the magnetic and proton-conductive properties\nof two sulfonated <b>CoHOF</b> and <b>MnHOF</b>, {M(H<sub>2</sub>O)<sub>2</sub>(abs)<sub>2</sub>}<sub><i>n</i></sub> (M = Co<sup>2+</sup> and Mn<sup>2+</sup>, Habs = 4-aminoazobenzene-4’-sulfonic\nanion), constructed by coordination chains. The supramolecular frameworks\nsustained by H bonds between −SO<sub>3</sub><sup>–</sup> and coordinated water show directional ladder-type H bonds with\nhydrophilic nanochannels, leading to high proton conduction with exceptionally\nhigh conductivity around 10<sup>–2</sup> S cm<sup>–1</sup> at 100 °C under 97% relative humidity. In particular, the maximum\nσ value of <b>CoHOF</b>, 2.11 × 10<sup>–2</sup> S cm<sup>–1</sup>, recorded the highest value among the reported\nproton-conducting materials showing slow magnetic relaxation. Meanwhile,\nthe molecular structure of organosulfonate enables the magnetic isolation\nof high-spin Co<sup>2+</sup> and Mn<sup>2+</sup> centers in the frameworks.\nMagnetic measurements indicated that the MHOFs show field-induced\nsingle-ion magnet (SIM) properties, making these compounds rare magnetic-proton-conductive\nMHOFs. The work provides not only two unique MHOFs with SIM behavior\nand high proton conduction performance but also avenues for designing\nstable bifunctional MHOFs via a coordination chain approach.