A Porous Europium Metal–Organic Framework as a Highly Sensitive Bifunctional Sensor for Isoprocarb and Levofloxacin

The development of highly sensitive luminescence sensing materials has attracted much attention in recent years. In this study, a new two-dimensional porous europium metal–organic framework (EuMOF, [Eu(DHDA)1.5·3H2O]n; DHDA = 2,2-dihydroxyacetic acid) is obtained, characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), luminescence, and Fourier transform infrared spectroscopy (FT-IR). At the best excitation at 295 nm, EuMOF shows red luminescence (CIE: 0.6255, 0.3740) and has four obvious peaks at 582, 605, 641, and 689 nm, which are due to 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4 transitions, respectively. Studies have shown that EuMOF is a stable, fast-responding, and highly sensitive luminescence sensor for isoprocarb and levofloxacin (Lvx) in aqueous solutions, apple peel and rice extract solutions, and real urine, which are closely associated with food safety and human health. The sensing behavior toward isoprocarb and Lvx may be attributed to the specific binding of the two analytes to EuMOF. The sensing of isoprocarb is a dynamic luminescence-quenching process, while that of Lvx is a dynamic luminescence-enhancing process. The limits of detection (LOD) for isoprocarb and Lvx are as low as 1.0 and 0.5 nM, respectively, which are much lower than the Chinese national standard (GB 28260-2011, 2.583 μM). EuMOF also demonstrates strong anti-interference detection of isoprocarb in apple peel and rice extract solutions, as well as Lvx in real urine, with excellent detection stability in a 0.01~9.0 nM range. The recovery rates for isoprocarb and Lvx in real samples are 99.12%~101.25%. This work provides the first bifunctional lanthanide sensor for pesticides and antibiotics.