Electrochemical Detection of Fluoride Ions Enhanced by 3-Aminophenylboronic Acid Manipulated MIL-100(Fe)/g-C3N4 Nanocomposite

The traditional analysis methods for fluoride ions, including potentiometric titration and chromatography, suffer from issues such as complex analysis processes, high costs, and long duration. Here, a typical nanocomposite, consisting of an iron metal–organic framework (MIL-100(Fe)) with surface defects and graphitic carbon nitride (g-C 3 N 4 ), has been successfully developed through regulation by 3-aminophenylboric acid, specifically for the fabrication of fluoride ion sensors. The electrochemical behavior of fluoride ions was investigated using the modified electrode via differential pulse voltammetry. The test results demonstrated a significant linear correlation between the intensity of response current and the concentration of fluoride ions, with an R 2 value greater than 0.9926, across two concentration ranges: 0.8–8.0 and 8.0–80 μM. The limit of detection and sensitivity for fluoride ions were calculated to be 0.20 μM and 17.007 μA μM –1 cm –2, respectively. Mechanism analysis reveals that the primary reason for the enhancement of the properties of the modified materials lies in the exposure of additional metal active sites due to the defect structure, as well as the synergistic effect of boric acid functional groups. The interference of several common anions, including Br –, I –, Cl –, NO 3 –, CO 3 2–, SO 4 2–, H 2 PO 4 – and CH 3 COO –, was found to be almost negligible. Additionally, the working electrode has also been preliminarily evaluated in tap water and lake water samples and obtained recoveries in the range of 92–108%.