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Highly Stable Acid-Induced Emission-Enhancing Cd-MOFs: Synthesis, Characterization, and Detection of Glutamic Acid in Water and Fe Ions in Acid

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journal contribution
posted on 19.04.2021, 07:14 by Chuanbin Fan, Bin Zhu, Xia Zhang, Caifeng Bi, Dongmei Zhang, Ziao Zong, Yuhua Fan
Two novel 3D fluorescent metal–organic frameworks (MOFs), [Cd­(L)­(bbibp)]n (1) and [Cd­(L)­(bbibp)0.5]n (2), where H2L = 4,4′-(4,4′-bipyridine-2,6-diyl)­dibenzoic acid and bbibp = 4,4′-bis­(benzoimidaz-1-yl)­biphenyl, were acquired through a conventional method and characterized via IR spectra, single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, powder X-ray diffraction (PXRD), scanning electron microscopy, N2 adsorption–desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The crystal framework of Cd-MOF 1 remained stable in the range of pH = 1.0–12.0. Interestingly, the emission peak of 1 showed a red shift and exhibited a fluorescence turn-on effect in an acidic environment. X-ray diffraction measurement revealed that the crystal structure of 1 remained unchanged after immersion in a pH = 1.0 solution. In addition, Cd-MOFs 1 and 2 displayed fluorescent quenching to l-glutamic acid with high sensitivity and selectivity. Meanwhile, 1 showed high selectivity in recognizing Fe3+ under acidic conditions, which made 1 capable of detecting Fe3+ in acidic industrial wastewater. Finally, the fluorescent sensing mechanism was carefully studied by PXRD, transient fluorescence lifetime, XPS, and UV spectroscopy.