Bisligand-coordinated cadmium organic frameworks as fluorescent sensors to detect Ions, antibiotics and pesticides in aqueous solutions

Three bisligand-coordinated two-dimensional or one-dimensional cadmium-based luminescent coordinated polymers, namely, [Cd3(BTC)2(DTP)(H2O)6]·(H2O)2.5 (1) (BTC = benzene-1,3,5-tricarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine); [Cd2(IPA)2(DTP)(H2O)4]·(H2O)3(DMF)2 (2) (IPA = isophthalic acid and DMF = dimethylformamide); and [Cd4(DFDA)4(DTP)2(H2O)8]·(H2O)17 (3) (DFDA = 2,5-dihydrofuran-2,5-dicarboxylic acid), were constructed by solvothermal synthesis. The obtained MOFs were characterized by employment of single crystal X-ray diffraction, powder XRD analysis, elemental analysis, IR, TGA and luminescence analysis. Fluorescence sensing experiments show that complexes 1–3 are effective and selective in sensing MnO4−, Fe3+ and Cr2O72−. For the analysis of antibiotics and pesticides, complex 1 exhibited the highest quenching rates for norfloxacin (NOR) and nitenpyram (NTP). For complexes 2–3, cefixime (CFX) and metamitron (MMT) caused the most obvious fluorescence quenching of all of the tested antibiotics and pesticides, respectively. During the sensing processes, both the inner filter effect (IFE) and fluorescence resonance energy transfer (FRET) play a key role in fluorescence quenching for all three complexes.