A boric acid functional multi-emission metal organic frameworks-based fluorescence sensing platform for visualization of gallic acid

Gallic acid (GA) is widely applied as antioxidant in food, beverages, health-care products, as well as medicines, quantification detection of GA is essential for human health and quality control in food, drugs and health-care products. Herein, we designed a portable sensing platform by utilizing multi-emission Europium Metal -Organic Frameworks (Eu-MOFs) fluorophore which constructed by the coordination polymerization of europium ions (Eu3+) with 3,5-Dicarboxybenzeneboronic acid (BBDC) for the visual detection of GA. The Eu-MOFs fluorophore displayed red fluorescence with the emission peaks at 454 nm and 615 nm under 270 nm excitation. With the addition of GA, the special covalent structure of the borate ester formed between the phenolic hydroxyl group of benzene ring with the hydroxyl group of the boric acid. The red emission at 615 nm decreased, while the blue emission at 454 nm increased gradually. The highly colorimetric fluorescence provides a significant color change from red to blue and furtherly improves the detection precision, resulting in a visual and rapid detection of GA with a limit of detection (LOD) of 22.0 nM. Furthermore, the Eu-MOFs fluorescent probe applied for visual and quantitative detection of GA combined with smartphone color recognizer in tea and fruit juice samples with the recovery range of 88.34-101.16 %, and the detection results were consistent with high performance liquid chromatography (HPLC) results, which suggest an effective strategy to monitor the food additives for food safety and health guarantee.