Constructing redox-active 3D covalent organic frameworks with high-affinity hexameric binding sites for enhanced uranium capture

The arduousness of nuclear waste disposal and the serious consequences of nuclear accidents motivate the development of efficient solid-phase extractants to provide enhanced protection. Herein, we report the first example of a hydroquinone-functionalized 3D covalent organic framework (DHBA-TAPM) with unique redox activity and high-affinity hexameric binding sites to be well suited as an efficient platform for selective capture and in situ reduction of radionuclide uranium. The high-affinity hexameric binding sites laced on the open 3D interconnected nanochannels showed high accessibility, and hollow tubular morphology enhanced the permeability, allowing greatly improved the utilization efficiency of the binding site. In addition, compared with adsorbents based on physical and/or chemical adsorption, the synergistic effect of the redox mineralization mechanism and high-affinity hexameric binding sites of DHBA-TAPM can significantly reduce the impact of binding site protonation under highly acidic conditions in chemisorption, thereby increasing the capture capacity. As a result, the DHBA-TAPM far outperform than other analogous adsorbents in terms of adsorption capacity and kinetics for uranium under highly acidic conditions. This work provides a facile strategy for the synthesis of functionalized 3D COFs and opens up the application of redox-active 3D COFs in environmental remediation.