Eu(III)-incorporated HOFs as a ratiometric and visualized probe for sensitive detection of anthrax biomarker

Due to the high virulence and lethal effects of Bacillus anthracis spores, the efficient and visualized detection for the primary spore biomarker, 2,6-pyridine dicarboxylic acid (DPA), is of particular importance. In this work, C₃-symmetric tris(4-carboxyphenyl)amine (TCA), was selected to construct a water-stable hydrogen-bonded organic framework (HOF-16) with partly-bare carboxyl groups. By the coordination of Eu³⁺ with the O atoms on carboxyl groups, the as-obtained hybrid material Eu³⁺@HOF-16 shows a single blue-emissive band derived from TCA. When exposed to DPA, the red characteristic emission of Eu³⁺ was significantly increased based on the coordication interaction and energy transfer between DPA and Eu³⁺. Meanwhile, the competitive absorption between DPA and TCA resulted in the decreased luminescence of TCA. Eu³⁺@HOF-16 was therefore developed as a turn-on and ratiometric fluorescence probe for DPA. The results showed that Eu³⁺@HOF-16 has a good linear response to DPA in the concentration range of 0-90 μM in aqueous solution, with excellent water stability, high sensitivity (limit of detection = 104 nM) and good selectivity. To conclude, the proposed strategy enables efficient and reliable DPA monitoring, exhibiting remarkable performance in pathogenic agent screening while addressing critical needs in water security and human health management.