Rapid Determination of Mercury Ions in Environmental Water Based on an N‐Rich Covalent Organic Framework Potential Sensor

In this article, an N‐rich covalent organic framework (COFTFPB‐TZT) was successfully synthesized using 4,4′,4′‐(1,3,5‐triazine‐2,4,6‐triyl) trianiline (TZT), and 4‐[3,5‐bis (4‐formyl‐phenyl) phenyl] benzaldehyde (TFPB). The as‐prepared COFTFPB‐TZT possesses irregular cotton wool patches with a large specific surface area. A novel selective electrode based on COF TFPB-TZT was used for the determination of Mercury ions. The abundance of N atoms in COF TFPB-TZT provides more coordination sites for Hg 2+ adsorption, resulting in a change in the surface membrane potential of the electrode to selectively recognize Hg 2+ . Under optimal experimental conditions, the ion‐selective electrode shows a good potential response to Hg 2+ , with a linear range of 1.0 × 10 −9 ∼1.0 × 10 −4 , a Nernst response slope of 30.32 ± 0.2 mV/‐PC at 25°C and a detection limit of 4.5 pM. At the same time, the mercury‐ion electrode shows a fast response time of 10 s and good reproducibility and stability. The selectivity coefficients for Fe 2+ , Zn 2+ , As 3+ , Cr 6+ , Cu 2+ , Cr 3+ , Al 3+ , Pb 2+ , NH 4 + , Ag + , Ba 2+ , Mg 2+ , Na + , and K + are found to be small, indicating no interference in the detection system. The proposed method can be successfully applied to the determination of Hg 2+ in 3 typical environmental water samples, with a recovery rate of 98.6–101.8%. In comparison with the spectrophotometric method utilizing dithizone, the proposed method is simple and fast and holds great potential application prospects in environmental water quality monitoring and other fields.