A Fluorescent Metal–Organic Framework for Food Real-Time Visual Monitoring

Due to increasing food-safety issues, exploiting efficient approaches for food quality assessment and instrumentation has attracted concerns worldwide. Herein, a smart evaluation system based on a fluorescent metal–organic framework (MOF) is developed for real-time visual monitoring of food freshness. Via post-synthetic modification, a ratiometric fluorescent MOF probe is constructed by covalently coupling fluorescein 5-isothiocyanate (5-FITC) with NH₂-rich lanthanide MOF. The probes exhibit a dual-emissive-responsive to biogenic amine, resulting in an increase in FITC emission along with a decrease in Eu³⁺ emission accompanied by a clear distinguishable color transition from orange red to green. After doping the probes on a flexible substrate, the obtained MOF composite film can be integrated with a smartphone-based portable platform easily. It is proved that this smart evaluation system can be used for on-site inspection of the freshness of raw fish samples. This work develops a fluorescent MOF-based smart evaluation system as a novel platform for application in food monitoring, which not only has enormous economic value but also holds great public health significance.