Preparation of covalent organic framework with carboxy and triazine for efficient removal of Pb2+ ions

Recently, the development of high-selectivity porous materials has attracted much attention due to the long-term accumulation of heavy metals in the aquatic environment. Covalent organic frameworks (COFs) show great potential as sustainable porous materials, possessing several properties that make them suitable for sewage purification and rapid adsorption. In this paper, two novel COFs containing triazine and carboxyl bifunctional groups, DAA-TFPT-COF and PDA-TFPT-COF, were developed. The DAA-TFPT-COF and PDA-TFPT-COF have high specific surface areas and good metal ion adsorption properties. Moreover, they have behaved good metal ion adsorption ability in not only acidic but also alkaline environments, which is superior to ordinary adsorption materials. The maximum adsorption amount of the DAA-TFPT-COF was up to approximately 128 mg g −1 for Pb 2+ ions. Additionally, the results of the simulation indicated that both COFs were consistent with the Langmuir adsorption model and the pseudo-second-order kinetic model, confirming the chemical adsorption process that occurs within the COFs. The strong adsorption effect in the COFs can be attributed to the electrostatic interactions between the COF and Pb 2+ ions. This also shows that the active affinity sites in the system play a crucial role in the metal ion capture process. DAA-TFPT-COF has a high partition coefficient, and exhibited fast adsorption kinetics, which makes it an excellent candidate for metal ion adsorption.