A Zn(II) metal−organic framework with organic fluorescent ligands and hydrogen-bonding network for effectively sensing Al3+ and Ga3+ ions, and proton conduction

Abstract

Energy shortage and environmental pollution become increasingly serious. Thus, there is urgent need to develop new functional materials to deal with these problems. Metal−organic frameworks (MOFs) are ideal candidates for fluorescence sensing pollutants and proton conduction. A benzothiadiazole-based three-dimensional (3D) Zn(II) MOF with the formula of {[(CH3)2NH2][Zn3(bbip)(BTDI)1.5(OH)]·DMF·MeOH·3H2O}n (JXUST-13, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and H4BTDI = 5,5′-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diisophthalic acid) with fluorescent ligands and rich hydrogen bond framework was used as a cation fluorescence sensor and proton conduction material. The fluorescence experiment revealed that JXUST-13 could detect Al3+ and Ga3+ ions by fluorescence blue shift and slight fluorescence enhancement. And it showed high sensitivity, good selectivity, anti-interference performance and cyclicity. The detection limits of JXUST-13 toward Al3+ and Ga3+ ions were 4.0 μM and 0.67 μM, respectively. Importantly, it could be rapidly detected by fluorescent test strips and naked eyes. The sensing mechanism may be due to the presence of electron transfer and the formation of exciplex. Proton conduction result indicated that the maximum conductivity value of JXUST-13 was 1.97 × 10−5 S·cm−1 at 80 °C and 98% RH. And the conductivity increased with humidity and temperature. The activation energy (Ea) value of JXUST-13 was 0.47 eV, which revealed the Vehicle mechanism. Therefore, JXUST-13 could be considered as a rare difunctional materials of blue-shifted fluorescence sensor for Al3+, Ga3+ ions and proton conduction.