Intercalation-Engineered MOF for Ultrasensitive Ratiometric Fluorescent Sensing of Enoxacin
The escalating global challenge of antibiotic contamination demands advanced sensing technologies for environmental monitoring and public health protection. Here, we present a structurally well-defined, intercalation-engineered metal-organic framework (MOF), HSB-W18, which functions as an ultrasensitive and selective fluorescence sensor for fluoroquinolone antibiotics. Single-crystal X-ray diffraction analysis unambiguously determined both the framework architecture and the spatial organization of intercalated 2,5-dihydroxyterephthalate molecules at atomic resolution. Through ultrasound-assisted synthesis, highly stable book-shaped microsheets (HSB-W18-MS) were obtained, maintaining exceptional aqueous dispersibility and luminescence intensity for over one month. These microsheets offer distinct advantages for antibiotic detection: specific recognition of diverse fluoroquinolones via unique fluorescence signatures; highly sensitive ratiometric detection of enoxacin (ENX) with a limit of detection (LOD) of 5.62 nM and rapid response kinetics (<30 s); exceptional selectivity alongside reusability. Systematic mechanistic investigations revealed a synergistic detection process involving multiple photophysical pathways. Furthermore, a smartphone-based portable detection system was successfully implemented, and the practical utility of the sensor was validated by quantifying ENX in complex environmental samples: tap water LOD = 18.32 nM and river water LOD = 29.87 nM. This study contributes to fundamental materials science and environmental monitoring by elucidating discernible structure-property relationships in intercalated MOFs, demonstrating a robust platform for field-deployable antibiotic detection and proposing an innovative design paradigm for environmental optical sensors.