Chemosensors Based on Lanthanide Metal–Organic Frameworks Showing Fluorescence Sensing for Malachite Green and 2,6-Pyridinedicarboxylic Acid

Lanthanide metal–organic frameworks (Ln-MOFs) have been widely applied in fluorescence detection due to their diverse structures and unique luminescence properties. In this work, two isostructural Ln-MOFs, namely, {[Ln2(THBA)(H2O)4]·2H2O}n (Ln = Eu for Eu-MOF and Tb for Tb-MOF, H6THBA = [1,1′4′,1″-terphenyl] −2′,3,3″,5,5′,5″-hexacarboxylic acid), were successfully synthesized and characterized. Fluorescence experiments demonstrate that Eu-MOF exhibits high sensitivity and selectivity toward malachite green (MG) and diphenylamine (DPA), with detection limits of 0.139 and 0.069 μM, respectively. Similarly, Tb-MOF also exhibits outstanding fluorescence sensing performance for MG and DPA, with detection limits of 0.089 and 0.094 μM, respectively. The fluorescent sensing films composed of Ln-MOFs@PMMA have been prepared by incorporating it into poly(methyl methacrylate) (PMMA), achieving rapid visual detection of MG and DPA. Moreover, highlighters with potential applications in anticounterfeiting were designed based on Eu-MOF and Tb-MOF.