Amino-Functionalized Single-Lanthanide Metal–Organic Framework as a Ratiometric Fluorescent Sensor for Quantitative Visual Detection of Fluoride Ions

Excessive content of fluoride ions (F-) in water will lead to water pollution and endanger human health, so the research on the method of low-cost, rapid, and efficient detection of F- is of particular significance. In this work, an amino-functionalized ligand with an appropriate triplet energy excited state, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4TPTC-NH2), was selected to construct a luminescent single-lanthanide metal-organic framework, EuTPTC-NH2, with uncoordinated amino groups for the detection of F-. Based on host-guest interactions, that is, hydrogen bonds formed between the free amino groups and F- ions, EuTPTC-NH2 was developed as a ratiometric fluorescence probe for F- detection with good anti-interference ability, low detection limit, high water stability, and selectivity. It was found that EuTPTC-NH2 has an excellent linear response to F- in the concentration range of 0-80 μM with high sensitivity and a low detection limit of 11.26 μM. A hydrogel membrane based on the combination of EuTPTC-NH2 and agarose was also prepared for the quantitative visual detection of F- in water.