Chain-based fluorescent TbIII metal–organic framework with good stability as a blue-shift and turn-on sensor toward H2PO4−†

Abstract

Dihydrogen phosphate (H₂PO₄⁻) in food and the environment is one of the major concerns for human health. Over the past few years, a large number of fluorescent metal–organic frameworks (MOFs) have been studied to explore desirable methods for selective analysis because fluorescence techniques have high sensitivity and are easy to operate. Herein, a chain-based MOF derived from Tb^III clusters {[Tb₃(BTDB)₃(μ₃-OH)₃(H₂O)]·solvents}_n (JXUST-52, H₂BTDB = (benzo[c][1,2,5]thiadiazole-4,7-diyl)dibenzoic acid) was successfully synthesized and structurally characterized. Single-crystal X-ray diffraction showed that three adjacent Tb^III ions were connected via carboxylate oxygen and μ₃-OH⁻, forming an infinite chain structure along the b axis. The neighbouring chains were linked by BTDB²⁻ ligands to finally form a chain-based 3D structure. JXUST-52 exhibited relatively good thermal and chemical stabilities and can specifically recognize H₂PO₄⁻ through luminescence enhancement and blue shift with a detection limit of 0.016 mM. Furthermore, the significant luminescence enhancement and blue shift under UV lamp irradiation were observable by the naked eye. The luminescence sensing mechanism is attributed to absorbance-induced enhancement between JXUST-52 and H₂PO₄⁻. In addition, lamp beads and test paper based on JXUST-52 were designed for the detection of H₂PO₄⁻ in practical application.