A Heterometallic Ag–Eu MOF: Sensitive Fluorescence Detection of 2-Methylhippuric Acid and High-Performance Proton Conduction

The functionalization of metal-organic frameworks (MOFs) enables fluorescence sensing and proton conduction, making them crucial in the fields of environmental monitoring and fuel cells. In this study, a heterometallic MOF of {[EuAg(TDA)₂(H₂O)]·H₂O}_n (<b>1</b>) was successfully constructed via a hydrothermal method using a thiodiglycolic acid (H₂TDA) ligand and Ag⁺/Eu³⁺ ions as metal centers. The structural characterization confirmed that <b>1</b> was a three-dimensional framework and exhibited good chemical stability. The fluorescence sensing experiments showed that <b>1</b> could be used as a fluorescence sensor for identifying 2-methylhippuric acid (2-MHA) with a detection limit as low as 16.6 nM, featuring rapidity, sensitivity, anti-interference, and good recycling performance, and its potential sensing mechanism had further been analyzed. Additionally, the electrical conductivity of <b>1</b> was 1.27 × 10^-3 S cm^-1 at 98% relative humidity and 333 K, indicating its potential as a proton conductive material. Hence, this multifunctional heterometallic MOF demonstrates significant application potential in both optical sensors and proton conductors.