| Summary: | A novel Zn(II) metal-organic framework [Zn<sub>4</sub>O(C<sub>30</sub>H<sub>12</sub>F<sub>4</sub>O<sub>4</sub>S<sub>8</sub>)<sub>3</sub>]<sub>n</sub>, namely <b>ZnBPD-4F4TS</b>, has been constructed from a fluoro- and thiophenethio-functionalized ligand 2,2′,5,5′-tetrafluoro-3,3′,6,6′-tetrakis(2-thiophenethio)-4,4′-biphenyl dicarboxylic acid (<b>H<sub>2</sub>BPD-4F4TS</b>). <b>ZnBPD-4F4TS</b> shows a broad green emission around 520 nm in solid state luminescence, with a Commission International De L’Eclairage (CIE) coordinate at x = 0.264, y = 0.403. Since d<sup>10</sup>-configured Zn(II) is electrochemically inert, its photoluminescence is likely ascribed to ligand-based luminescence which originates from the well-conjugated system of phenyl and thiophenethio moieties. Its luminescent intensities diminish to different extents when exposed to various metal ions, indicating its potential as an optical sensor for detecting metal ion species. Furthermore, <b>ZnBPD-4F4TS</b> and its NH<sub>4</sub>Br-loaded composite, <b>NH<sub>4</sub>Br@ZnBPD-4F4TS</b>, were used for proton conduction measurements in different relative humidity (RH) levels and temperatures. Original <b>ZnBPD-4F4TS</b> shows a low proton conductivity of 9.47 × 10<sup>−10</sup> S cm<sup>−1</sup> while <b>NH<sub>4</sub>Br@ZnBPD-4F4TS</b> shows a more than 25,000-fold enhanced value of 2.38 × 10<sup>−</sup><sup>5</sup> S cm<sup>−1</sup> at 40 °C and 90% RH. Both of the proton transport processes in <b>ZnBPD-4F4TS</b> and <b>NH<sub>4</sub>Br@ZnBPD-4F4TS</b> belong to the Grotthuss mechanism with <i>E</i><sub>a</sub> = 0.40 and 0.32 eV, respectively.
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