Fluorescent detection of S2− based on ZnMOF-74 and CuMOF-74

The detection of S2− is of great significance because excess S2− can lead to a variety of serious physiological diseases. Here, two metal-organic frameworks (MOFs), ZnMOF-74 and CuMOF-74, were synthesized by using 2,5-dihydroxy terephthalic acid with strong fluorescence as organic ligand and Zn2+ or Cu2+ as central coordination ions for S2− detection. Both as-prepared ZnMOF-74 and CuMOF-74 displayed nanospheres with a diameter of about 100 nm. Under the excitation of 353 nm, the ZnMOF-74 had a characteristic emission peak at 537 nm and the CuMOF-74 had a characteristic emission peak at 528 nm under excitation of 356 nm. The interaction of S2− and Zn2+ weakened the fluorescence of ZnMOF-74 but the interaction of S2− with Cu2+ to form CuS restored the fluorescence of CuMOF-74, so the ZnMOF-74 and CuMOF-74 were exploited as a fluorescent nanosensor for sensing S2−. The ZnMOF-74 sensor has a good linear range of 19.6 nmol L−1-90.0 μmol L−1, and the limit of detection was as low as 6.53 nmol L−1. The CuMOF-74 sensor has a good linear relationship with II0 in the S2− concentration range of 1.50 nmol L−1-125 μmol L−1, and the limit of detection was 1.50 nmol L−1. The proposed ZnMOF-74 and CuMOF-74 sensor could also detect S2− in actual samples.