3D Viologen-based covalent organic framework for selective and efficient adsorption of ReO4−/TcO4−

Due to the long half-life and high environmental mobility, the selective and efficient capture of TcO4− from nuclear effluents is very important, but it is still very challenging. Herein, we design and synthesize a novel three-dimensional (3D) cationic covalent organic framework (TFAM-BDNP) via Zincke reaction for selective capture of TcO4−/ReO4−. TFAM-BDNP exhibits high adsorption capacity (998 mg g−1) and extremely fast exchange kinetic (60 s) for ReO4− (the non-radioactive alternative to TcO4−), attributing to the open 3D hydrophobic channels, abundant active sites, and high chemical stability. More importantly, TFAM-BDNP shows good adsorption performance for ReO4− in the presence of significant excess competing anions with a wide pH value range of 2 to 12. Under complex simulated Hanford flow sample, TFAM-BDNP has outstanding removal efficiency of ReO4−. The adsorption mechanism of ReO4− is mainly caused by anion exchange process. This study provides a novel adsorbent for efficient capture of TcO4−/ReO4− in complex environmental systems and exploits an effective strategy for broadening the types of 3D COFs.