Modulating Uranium Extraction Performance of Multivariate Covalent Organic Frameworks through Donor–Acceptor Linkers and Amidoxime Nanotraps

Abstract

Covalent organic frameworks (COFs) can be designed to allow uranium extraction from seawater by incorporating photocatalytic linkers. However, often sacrificial reagents are required for separating photogenerated charges which limits their practical applications. Herein, we present a COF-based adsorption-photocatalysis strategy for selective removal of uranyl from seawater in the absence of sacrificial reagents. A series of ternary and quaternary COFs were synthesized containing the electron-rich linker 2,4,6-triformylphloroglucinol as the electron donor, the electron-deficient linker 4,4′-(thiazolo[5,4- d ]thiazole-2,5-diyl)dibenzaldehyde as the acceptor, and amidoxime nanotraps for selective uranyl capture (with the quaternary COFs incorporating [2,2′-bipyridine-5,5′-diamine-Ru(Bp) 2 ]Cl 2 as a secondary photosensitizer). The ordered porous structure of the quaternary COFs ensured efficient mass transfer during the adsorption-photocatalysis capture of uranium from seawater samples, with photocatalytically generated electrons resulting in the reduction of adsorbed U(VI) to U(IV) in the form of UO 2 . A quaternary COF, denoted as COF 2-Ru-AO, possessed a high uranium uptake capacity of 2.45 mg/g/day in natural seawater and good anti-biofouling abilities, surpassing most adsorbents thus far. This work shows that multivariate COF adsorption-photocatalysts can be rationally engineered to work efficiently and stably without sacrificial electron donors, thus opening the pathway for the economic and efficient extraction of uranium from the earth’s oceans.

Tuning excited state electronic structure and charge transport in covalent organic frameworks for enhanced photocatalytic performance

“…Discovering sustainable ways of harvesting uranium from seawater is critical to ensuring a reliable supply of uranium fuel for future generations (as well as being of importance in the treatment of wastewater from the nuclear industry and contaminated groundwater). COF-based adsorbent-photocatalyst systems are now being pursued for uranium extraction 46 – 48 . To date, the developed systems have relatively low activity for U(VI) reduction and/or need sacrificial reagents for separating photo-generated charges.…”

Hierarchical Cu-MOF hollow nanowire modified copper mesh for efficient antibacterial PM filtration

“…It is generally accepted that copper ions cause a sequence of events that eventually lead to cell death. 55–58 The antibacterial mechanism of the CHM and CMM here could also be attributed to the release of Cu 2+ ions, which initially adsorb on the cell membrane of bacteria and then infiltrate into the cells through interactions with the hydroxyl groups of peptidoglycans, causing damage to the cell membranes and DNA breakage. The SEM images were further used to observe visually the morphological changes of E. coli and S. aureus after antibacterial experiments for CMM-70 (Fig.…”

Amidoxime-Based Polymer Microspheres with High Selectivity for Uranium from Saline Lake Brine

“…We believe that once the formation of PAN can be widely avoided, using other monomers for copolymerization is also feasible. From the perspective of experiments and theoretical calculation, recent reports suggested that the adsorption strength of amidoxime for uranium is almost the highest. ,− Furthermore, the adsorption capacity of A-1 for uranium was 9.1 times higher than that of vanadium, while that of A-3 was 14.8 times. This may be due to the long distance between amidoxime groups on A-1 and the less modification amount of amidoxime.…”