A novel covalent organic framework with abundant N-O-O and N-N-O sites for detection and removal of Zn2+, Cd2+, Pb2+, Cu2+, and Hg2+

Here, tripolycyanamide (TPA) and 2,5-dihydroxyterephthalic acid (DDTA) were used to synthesize crystalline covalent organic framework (COFDDTA-TPA) which was employed to detect and remove heavy metal ions (HMIs). COFDDTA-TPA has abundant N-O-O and N-N-O sites and large specific surface area, which can be used as an excellent adsorbent for HMIs. The detection limits for Zn2+, Cd2+, Pb2+, Cu2+, and Hg(2+)were 0.85 nM, 0.096 nM, 0.14 nM, 0.072 nM, and 0.084 nM, respectively. The COFDDTA-TPA was controllably grown on both melamine foam (MF) and macroporous carbon to remove Cd2+, Pb2+, Cu2+, and Hg2+ effectively, which avoided some defects of traditional COFs powder such as random orientation, easy accumulation, and poor reproducibility. The COFDDTA-TPA/MF was further prepared as a water filter device for the removal of HMIs. In addition, the proposed material can detect and remove HMIs in sewage, soil, and blood serum real samples and showed great potential in environmental remediation.

Automated summary

In this study, COFDDTA-TPA was synthesized using TPA and DDTA, and it was found to have abundant sites and large surface area, making it an excellent adsorbent for heavy metal ions. By growing COFDDTA-TPA on a supporting material, effective removal of heavy metal ions was achieved, and the material was successfully applied in real samples.