Abstract
Uranium is a key element in the nuclear industry, but its unintended leakage has caused health and environmental concerns. Here we report a sp2 carbon-conjugated fluorescent covalent organic framework (COF) named TFPT-BTAN-AO with excellent chemical, thermal and radiation stability is synthesized by integrating triazine-based building blocks with amidoxime-substituted linkers. TFPT-BTAN-AO shows an exceptional UO22+ adsorption capacity of 427 mg g−1 attributable to the abundant selective uranium-binding groups on the highly accessible pore walls of open 1D channels. In addition, it has an ultra-fast response time (2 s) and an ultra-low detection limit of 6.7 nM UO22+ suitable for on-site and real-time monitoring of UO22+, allowing not only extraction but also monitoring the quality of the extracted water. This study demonstrates great potential of fluorescent COFs for radionuclide detection and extraction. By rational designing target ligands, this strategy can be extended to the detection and extraction of other contaminants.
Highlights
C=N-OH O 1sObserved Curve fitting Background C=N-OH O-U NH 2 N HOUO22+ in terms of saturated adsorption capacity as compared to porous organic polymers (POPs)-TB-AO, suggesting the important role of the adsorbent’s architecture
The results show that TFPT-BTAN-AO has superior stability in high concentration nitric acid compared with β-ketoenamine covalent organic framework (COF)
We studied the sensing performance of our COF
Summary
UO22+ in terms of saturated adsorption capacity as compared to POP-TB-AO, suggesting the important role of the adsorbent’s architecture. The results verified that the uranium extraction performance of TFPT-BTAN-AO was almost unchanged after treatment under various extreme conditions, indicating that TFPTBTAN-AO has excellent stability and practical application potential. This feature is a significant advantage over imine-based COFs sorbents that typically suffer from the decomposition of structures under extreme conditions[1,3]. It is worth noting that TFPT-BTAN-AO can be cycled at least six times without noticeable influence of response to UO22+ or sensitivity, and this exceptional regeneration can be observed by the naked eye under a portable UV lamp (Supplementary Fig. 30) This is the first demonstration of COF-based regenerable detection and extraction of UO22+. Such regeneration is almost impossible for previously reported imine-based COFs adsorbents
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