A novel covalent-organic framework for highly sensitive detection of Cd2+, Pb2+, Cu2+ and Hg2+

A novel covalent-organic framework (COFMELE-BTDD) containing multiple heavy metal ions (HMIs) adsorption sites was synthesized and applied to electrochemical sensing HMIs and Hg2+ adsorption. The COFMELE-BTDD was prepared by amine-aldehyde condensation of 2,5,8-triamino-s-heptazine (MELE) and 4,4'-(benzo[c] [1,2,5] thiadiazole-4,7-diyl)dibenzaldehyde (BTDD). The COFMELE-BTDD is a two-dimensional crystal nanosheet with highly ordered conjugated structure, and the pore size is 3.7 nm. A novel electrochemical sensor for the determination of Cd2+, Pb2+, Cu2+, Hg2+ was constructed with COFMELE-BTDD. Each unit of COFMELE-BTDD has multiple active sites for HMIs (N-S-N, -C=N), which can sensitively capture HMIs. The influence of experimental parameters (the amount of COFMELE-BTDD, pH value of electrolyte, deposition time and deposition potential) on electrochemical sensor was studied. The detection limits of Cd2+, Pb2+, Cu2+, Hg2+ are 0.00474 mu M, 0.00123 mu M, 0.00114 mu M, 0.00107 mu M, respectively. The sensitivities are 105.0 mu A mu M-1 cm(-2), 405.5 mu A mu M-1 cm(-2), 439.0 mu A mu M-1 cm(-2) and 465.1 mu A mu M-1 cm(-2). The sensor has good stability, reproducibility and anti interference ability. The COFMELE-BTDD can effectively remove Hg2+ in water samples. The results show that the COFMELE-BTDD has great potential in adsorption and detection of HMIs.

Automated summary

In this study, a novel covalent-organic framework, COFMELE-BTDD, was synthesized and utilized for electrochemical sensing of heavy metal ions (HMIs) and Hg2+ adsorption. The COFMELE-BTDD demonstrated excellent sensitivity and stability towards Cd2+, Pb2+, Cu2+, and Hg2+. The results show that the COFMELE-BTDD has great potential in the adsorption and detection of HMIs.