Pyrazinoquinazoline‐Based Eu‐MOF Ratiometric Fluorescence Sensing: Real‐Time Monitoring of Meat Spoilage Enabled by Dynamic Regulation of LMCT/LLCT Triggered by Biogenic Amines

Abstract This study develops a dual‐emission Eu‐MOF ratiometric fluorescence sensor for biogenic amine detection in food spoilage monitoring. The sensor exhibits dual emission at 495 nm (ligand π→π* transition) and 615 nm (ligand‐to‐metal charge transfer, LMCT) through the antenna effect. Biogenic amines specifically regulate the intensity ratio (I 495nm /I 615nm ) by adsorbing into MOF pores via hydrogen bonding, triggering a dynamic equilibrium switch between LMCT and ligand‐to‐ligand charge transfer (LLCT), causing fluorescence color shift from orange to green. Theoretical calculations reveal this response mechanism for the first time. Encapsulating Eu‐MOF in agarose hydrogel‐based portable tags with smartphone RGB analysis enables rapid quantitative detection of biogenic amines (detection limit: 3.7–9.1 µM, response time <10 min). The sensor allows real‐time tracking of spoilage in shrimp and chicken stored at 0–25 °C, with visual fluorescence color transitions reflecting amine accumulation levels. This work provides molecular insights into dynamic charge transfer regulation and establishes a high‐sensitivity, visual, wearable solution for on‐site food safety detection, advancing smart sensing technology in the food industry.