Multi-emission metal-organic frameworks for ratiometric detection of tetracycline antibiotics

The overuse of tetracycline (TC) antibiotics causes food residues that threaten human health. This study introduces a Zr-based dual-ligand fluorescent MOF, Eu@Zr-bpydc-L1, with post-synthetic Eu³⁺ doping for rapid ratiometric fluorescent detection of TC. The sensor shows a blue-to-red fluorescence shift, with a linear response from 0.028 μM to 28 μM and a detection limit of 0.014 μM. The ratiometric mechanism involves antenna effect induced red emission enhancement, and blue emission quenching through inner filter and photoinduced electron transfer effects. Test strips made by dropping the MOF onto filter paper enable on-site TC detection using a smartphone. Combined with machine learning, a fluorescent sensor array composed of three variants of Eu@Zr-bpydc-L1/L2/L3 can distinguish four different TC antibiotics with 99.5% accuracy. This work provides a sensitive and selective method for TC detection and highlights the potential of ratiometric fluorescent MOFs and machine learning in food safety and public health.