超稳定偕胺肟功能化共价有机框架用于高效选择性海水提铀
海水提铀对于核能生产具有战略性意义。偕胺肟基功能性吸附剂在海水铀提取中发挥着不可或缺的作用。然而，面对海水复杂的离子环境，尤其在钒离子的存在下，同时获得高吸附性能和高选择性是一个巨大挑战。华北电力大学环境科学与工程学院王祥科教授课题组制备了基于聚芳醚的开环偕胺肟功能化共价有机框架(COF-HHTF-AO)，COF-HHTF-AO表现出高结晶度和优异的化学稳定性。COF-HHTF-AO在真实海水中对铀的提取量高达5.12 mg/g，是钒的1.61倍。理论计算研究发现，铀相比于钒的高选择性归因于其与偕胺肟的结合方式和配位形态。COF-HHTF-AO具有高吸附容量、优异的选择性和超高稳定性，是一种具有广泛前景的海水提铀吸附剂。相关研究成果以封面文章“Extremely stable amidoxime functionalized covalent organic frameworks for uranium extraction from seawater with high efficiency and selectivity”发表于Science Bulletin 2021年第19期。
Fig. 1 Scheme of the fabrication of COF-HHTF and COF-HHTF-AO and their chemical structure characterization. (a) Synthesis of COF-HHTF and COF-HHTF-AO. The 13C CP-MAS solid-state NMR spectrum of COF-HHTF (b) and COF-HHTF-AO (c).
Fig. 2 Crystallographic characterization and stability evaluation of COF-HHTF and COF-HHTF-AO. PXRD patterns of COF-HHTF (a) and COF-HHTF-AO (b), Experimental spectrum (black), smoothed line (red), and simulated pattern based on AA stacking model (purple) are shown. AA stacking structural representations of COF-HHTF (c) and COF-HHTF-AO in top (upper) and side (bottom) views, the numbers denote the simulated interlayer distance. FT-IR spectra (e) and PXRD profiles (f) of COF-HHTF-AO before and after treatment under different harsh conditions.
Fig. 3 Uranium adsorption experiments in aqueous solution and binding mechanism investigation. (a) Effect of pH on the uranium adsorption efficiency and (b) Uranium sorption isotherms for COF-HHTF and COF-HHTF-AO. (c) High-resolution XPS spectra of O 1s for COF-HHTF-AO before and after the uranium extraction. (d) The uranium adsorption efficiency of COF-HHTF and COF-HHTF-AO in five successive reusing cycles. The error bars indicate standard deviations in three replicates.
Fig. 4 Uranium adsorption selectivity in simulated seawaters and real seawater samples. (a) Influence of high concentration (0.2 mol/L) coexisting cations and anions on the uranium adsorption efficiency of COF-HHTF and COF-HHTF-AO. (b) Binding selectivity to 100 times concentrated coexisting interfering metal ions in natural seawater. (c) Uranium adsorption kinetics of COF-HHTF-AO in natural seawater spiked with 1 and 10 ppm uranium. The inset image is the pseudo-second-order model fitted results. (d) Adsorption capacity of COF-HHTF-AO towards uranium and competitive metals in natural seawater. The error bars indicate standard deviations in three replicates.
Fig. 5 Interaction configuration and binding mechanism between U(VI) or V(V) and COF-HHTF-AO based on DFT simulation. The optimized interaction structures of COF-HHTF-AO with uranyl in the presence of different carbonate contents (a) and two forms of vanadium oxide (HVO42− and H2VO4−) (b), which are neutralized by Na ions, bond lengths are in Å. (c) Charge density difference of the stable configuration of uranyl, HVO42−, and H2VO4− adsorbed on COF-HHTF-AO. The yellow and cyan regions represented that charge density increased and decreased, respectively.
Gong Cheng, Anrui Zhang, Zhiwei Zhao, Zimin Chai, Baowei Hu, Bing Han*, Yuejie Ai*, Xiangke Wang*. Extremely stable amidoxime functionalized covalent organic frameworks for uranium extraction from seawater with high efficiency and selectivity. Science Bulletin, 2021, 66(19): 1994-2001
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