Eu(III)-based metal-organic-frameworks luminescent probe and its sensing properties for nitrobenzene and Cu(II)

A novel europium metal-organic frameworks (Eu-MOFs), based on 1,3,5-benzotricarboxylic acid (H 3 BTC), 4,4′-azopyridine (4,4′-AZ) and N , N -dimethyllformamide (DMF), was synthesized by the solvothermal method . The crystal structure, thermal stability, morphology and luminescent properties are characterized by the X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and optical spectroscopic techniques. The Eu-MOFs display a unique luminescence quenching effect to nitrobenzene (NB) and copper (Cu 2+ ) ions. The turn-off luminescence can be induced by 210 ​ppm NB or by 1000 ​μM Cu 2+ ions. Furthermore, the high sensitivities ( K SV  ​= ​0.039 ​ppm −1 for NB, and K SV =0.029 ​μM −1 for Cu 2+ ) and low detection limits (0.656 ​ppm for NB, and 1.395 ​μM for Cu 2+ ) are obtained. The sensing mechanisms are reasonably explained based on the electron and energy transfer. The experimental results show that the Eu-MOFs can be used as a potential sensing luminescence quenching probes for NB and Cu 2+ ions.