Dual Turn-On/Off Fluorescence Sensing in Heterobimetallic MOFs for Ultrasensitive Detection of Multiple Antibiotics

The development of dual fluorescence sensors is crucial for reliable and sensitive antibiotic detection. This study reports two isostructural heterobimetallic metal–organic frameworks (MOFs), which are formulated as {[(CH3)2NH2]2[Zn2M(O)2(BTC)2]·2H2O}n (M = Co (1), Ni (2), and H3BTC = 1,3,5-benzenetricarboxylic acid) with a (3,6)-connected three-dimensional (3D) dual-channel framework, showing excellent chemical stability and tunable fluorescence. Notably, these MOFs enable ultrasensitive sensing of chloramphenicol (CAP), nitrofurantoin (NFT), nitrofurazone (NFZ), and tetracycline (TC). Density functional theory (DFT) simulations show CAP adsorbs on the compound 1 surface through hydrogen bonding, without FRET. Conversely, NFT, NFZ, and TC quenching involves competitive adsorption and FRET. The dual fluorescence sensors enable ultrasensitive detection, with limits of detection (LOD) for CAP reaching 108.70 ppm (Compound 1, Zn/Co-MOF) and 142.70 ppm (Compound 2, Zn/Ni-MOF). For quenching-based detection, sub-30 ppm sensitivity is achieved: NFT (29.80 ppm for 1; 28.40 ppm for 2), NFZ (26.30 ppm for 1 and 27.90 ppm for 2), and TC (24.70 ppm for 1 and 43.40 ppm for 2). Furthermore, the sensor demonstrates superior anti-interference capabilities and consistent performance in complex environments, such as tap water and milk. This work not only pioneers a heterobimetallic design strategy for tunable MOF-based sensors but also demonstrates their practical utility in environmental monitoring and food safety.