An Eu-MOF Platform for Simultaneous Fluorescent Sensing of Chloramphenicol and 3,3'-Dimethoxybenzidine

Abstract A new europium-based metal−organic framework (MOF), namely [Eu4(L)2(NMP)4(H2O)4]·(H2O)4 (1), was successfully synthesized via a solvothermal reaction of Eu3+ ions with the multicarboxylate ligand 4′,4″,4‴-nitrilotris((1,1′-biphenyl)-3,5-dicarboxylic acid) (H6L). Structural analysis revealed that 1 possesses an extended porous framework and exhibits dual fluorescence emissions originating from ligand-centered emission at 450 nm and characteristic Eu3+ emission at 615 nm upon excitation at 295 nm. Benefiting from the dual-emission feature, 1 can serve as a fluorescent sensor for the sensitive detection of chloramphenicol (CAP) and 3,3′-dimethoxybenzidine (3,3-DMB). Upon the addition of CAP, the characteristic Eu3+ emission at 615 nm was significantly quenched, whereas 3,3-DMB induced a distinct ratiometric fluorescence response with enhanced ligand-centered emission and decreased Eu3+ emission. The corresponding detection limits were determined to be 199.5 nM for CAP and 44 nM for 3,3-DMB, respectively. In addition, 1 exhibits excellent selectivity, anti-interference capability, and recyclability. Mechanistic investigations revealed that the sensing behavior toward CAP originates from the synergistic effect of the inner filter effect (IFE) and photoinduced electron transfer (PET), while the fluorescence response toward 3,3-DMB is attributed to the combined contribution of the inner filter effect (IFE) and modulation of the ligand-to-metal energy transfer process. This work demonstrates the potential application of dual-emissive lanthanide MOFs for rapid and sensitive fluorescence detection of hazardous analytes.