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It has been considered challenging to develop ideal adsorbents for efficient and lower adsorption time uranium extraction, especially 3D covalent organic frameworks with interpenetrating topologies and tunable porous structures. Here, a "soft" three-dimensional (3D) covalent organic framework (TAM-DHBD) with a fivefold interpenetrating structure is prepared as a novel porous platform for the efficient extraction of radioactive uranium. The resultant TAM-DHBD appears exceptional crystallinity, prominent porosity and excellent chemical stability. Based on the strong mutual coordination between phenolic-hydroxyl/imine-N on the main chain and uranium, TAM-DHBD can effectively avert the competition of other ions, showing high selectivity for uranium extraction. Impressively, the 3D ultra-hydrophilic transport channels and multi-directional uniform pore structure of TAM-DHBD lay the foundation for the ultra-high-speed diffusion of uranium (the adsorption equilibrium can be reached within 60 min under a high-concentration environment). Furthermore, the utilization of lightweight structure not only increases the adsorption site density, but renders the adsorption process flexible, achieving a breakthrough adsorption capacity of 1263.8 mg g

Uranium is a key element in the nuclear industry and also a global environmental contaminant with combined highly toxic and radioactive. Currently, the materials based on post-modification of amidoxime have been developed for uranium detection and adsorption. However, the affinity of amidoxime group for vanadium is stronger than that of uranium, which is the main challenge hindering the practical application of amidoxime-based adsorbents. Herein, we synthesized a fluorescent covalent organic framework (TFPPy-BDOH) through integrating biphenyl diamine and pyrene unit into the π-conjugated framework. TFPPy-BDOH has an excellent selectivity to uranium due to the synergistic effect of nitrogen atom in the imine bond and hydroxyl groups in conjugated framework. It can achieve ultra-fast fluorescence response time (2 s) and ultra-low detection limit (8.8 nM), which may be attributed to its intrinsic regular porous channel structures and excellent hydrophilicity. More excitingly, TFPPy-BDOH can chemically reduce soluble U (VI) to insoluble U (IV), and release the binding site to adsorb additional U (VI), achieving high adsorption capacity of 982.6 ± 49.1 mg g-1. Therefore, TFPPy-BDOH can overcome the challenges faced by current amidoxime-based adsorbents, making it as a potential adsorbent in practical applications.

Uranium is an important element in the nuclear industry while the discharge of radioactive wastewater can cause serious damages to the environment. In this work, an ultra-stable sp

Uranium is an important element in the nuclear industry while the discharge of radioactive wastewater can cause serious damages to the environment. In this work, an ultra-stable sp2 carbon-conjugated covalent organic framework (COF-PDAN-AO) is synthesized with amidoxime-substituted monomers for detection and efficient adsorption of uranium from radioactive wastewater. Abundant amidoxime groups laced on the open 1D channels of COF-PDAN-AO exhibit exceptional accessibility and the regular pores facilitate the mass transfer. Based on these features, COF-PDAN-AO achieves ultra-low detection limit of 6.5 nM, high uranium adsorption capacity (410 mg/g) and selective interaction with uranium. In addition, various spectroscopies verify COF-PDAN-AO possesses excellent radioresistance in acidic solution. Regeneration studies have shown that COF-PDAN-AO maintained good structural stability after seven cycles. These results indicate that our sp2 carbon conjugated COF can be potentially used for practical detection and adsorption of uranium from radioactive wastewater. This strategy can be extended to detection and extraction of other contaminants by designing the target ligand.