Ratiometric photoluminescent sensing of 2,6-pyridinedicarboxylic acid using bimetallic metal–organic framework nanorods

Lanthanide-based metal–organic frameworks (MOFs) are promising probes for photoluminescent sensing of various chemical substances. In this study, we report the ultrasonication-assisted synthesis of bimetallic Eu/Tb-MOF nanorods for the highly sensitive detection of 2,6-pyridinedicarboxylic acid (DPA), a major biomarker for Bacillus anthracis. The prepared Eu/Tb-MOF nanorods exhibited a robust framework structure, uniform morphology, and strong photoluminescent emissions thanks to the synergy between Eu³⁺ and Tb³⁺ ions. The photoluminescent quenching effect is clearly observed upon the addition of DPA to these Eu/Tb-MOF aqueous suspensions, and has been utilized for sensing DPA. We achieved an impressive detection limit of 60 nM using the Eu_0.1Tb_0.9BTC MOF with a low concentration of 20 mg L⁻¹ in aqueous solvent, attributed to the unique energy transfer process from DPA to the Eu/Tb luminescent centers. The various factors which affect sensing performance including material system, lanthanide composition, DPA concentration, type of solvent and interferences were investigated. This work provides an efficient route for the synthesis of Eu/Tb-MOF nanorods as highly sensitive and selective photoluminescent sensors for DPA detection.