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.

Automated summary

In this study, a novel three-dimensional cationic covalent organic framework (TFAM-BDNP) was designed and synthesized via Zincke reaction for the selective capture of TcO4-/ReO4-. TFAM-BDNP exhibited high adsorption capacity and extremely fast exchange kinetic for ReO4-, attributed to its open 3D hydrophobic channels, abundant active sites, and high chemical stability. Furthermore, TFAM-BDNP showed good adsorption performance for ReO4- in the presence of competing anions and under a wide pH value range, indicating its potential for efficient capture of TcO4-/ReO4- in complex environmental systems.