Terbium(iii)-based coordination polymer with millimeter-size single crystals and high selectivity and sensitivity for folic acid

Folic acid (FA), as a water-soluble vitamin B compound, plays an irreplaceable role in human health. It is crucial to detect FA in a rapid, efficient, and sensitive way. In the current study, we constructed a fluorescence coordination polymer (CP) from Tb^III and pyridine-2,6-dicarboxylic acid (H₂pda) to detect folic acid. Single crystal X-ray diffraction indicated that the complex contained a one-dimensional (1D) double-chain structure, which assembled into a three-dimensional (3D) supramolecular framework via the inter-chain hydrogen bonds. Interestingly, the crystal size of the complex was optimized up to 2.4 mm through L₉(3⁴) orthogonal experiments. The complex exhibited typical Tb^III fluorescence, which could detect FA with high detection sensitivity (LOD = 0.22 μM), an excellent anti-interference ability, and remarkable recyclability in aqueous solution through fluorescence quenching of the emission spectra. Fluorescence quenching is related to the competition absorption (CA) and photoinduced electron transfer (PET) process between the complex and FA, which is inspected by density functional theory (DFT) calculations.