Construction of a novel magnetic metal–organic framework fluorescent sensor for selective detection and magnetic separation of 4-nitrophenol

The development of a sensitive and selective fluorescent sensor for 4-nitrophenol (4-NP) is very important for ensuring environmental and ecological security. Herein, a novel fluorescent sensor using a magnetic metal-organic framework (Fe₃O₄@SiO₂@MOF) has been constructed specifically for detecting and magnetically separating 4-NP in real water samples. The synthesized Fe₃O₄@SiO₂@MOF was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TG), X-ray diffraction spectroscopy (XRD), magnetic saturation intensity measurement and N₂ adsorption-desorption analysis. The prepared Fe₃O₄@SiO₂@MOF presented a core-shell structure and good thermal-stability. Under optimum conditions, Fe₃O₄@SiO₂@MOF exhibits a rapid response in detecting 4-NP within 30 s, satisfactory selectivity and magnetic properties, outstanding reusability and excellent stability. Furthermore, a wide linear range of 5.0-200 μM with a detection limit of 2.2 μM was attained. In addition, real water samples were successfully analyzed with Fe₃O₄@SiO₂@MOF. The spiked recoveries and the relative standard deviation were 92.2-104.8% and 1.2-3.3%, respectively. Overall, this strategy provides new sights into the construction of practical fluorescent sensors for sensitive and selective detection of 4-NP in environmental samples.