A Multifunctional Luminescent Tb-MOF for Selective Fluorometric Detection of Cr(VI) and Steroid Hormones

Metal-organic frameworks (MOFs) have attracted considerable attention as luminescent materials for chemical sensing due to their structural tunability, high sensitivity, and rapid response. In this study, a terbium-based metal-organic framework (Tb-MOF) was synthesized via a solvothermal method using 3,4-pyridinedicarboxylic acid and 1,10-phenanthroline as organic ligands. The structural and morphological properties of the synthesized material were characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The photoluminescence properties of Tb-MOF were investigated using fluorescence spectroscopy under UV excitation. The sensing performance of the material was evaluated toward various analytes, including metal ions, common anions, and representative hormone molecules. The Tb-MOF exhibited a strong green emission centered at approximately 544 nm and showed pronounced fluorescence quenching in the presence of Cr(VI) ions. In contrast, most other tested metal ions and anions produced negligible changes in fluorescence intensity. Quantitative analysis revealed a Stern-Volmer quenching constant (K_sv) of 3.37 × 10³ M^- 1 for Cr(VI), with a detection limit of 5.18 mg L^- 1. In addition, selective fluorescence quenching was observed for progesterone (P4) and estradiol (E2) among the tested hormone molecules, demonstrating nanomolar-level detection capability. These results indicate that the synthesized Tb-MOF is a promising luminescent sensor for the selective detection of Cr(VI) ions and certain steroid hormones, highlighting its potential applicability in environmental monitoring and biochemical sensing.