The uranium level in seawater is ≈1000 times as high as terrestrial ores and can provide potential near‐infinite fuel for the nuclear energy industry. However, it is still a significant challenge to develop high‐efficiency and low‐cost adsorbents for massively extracting uranium from seawater. Herein, a simple and fast method through low‐energy consumption sunlight polymerization to direct fabrication of a poly(amidoxime) (PAO) hydrogel membrane, which exhibits high uranium adsorption capacity, is reported. This PAO hydrogel owns semi‐interpenetrating structure and a hydrophilic poly(acrylamide) 3D network of hydrogel which can disperse and fix PAOs well. As a result, the amidoxime groups of PAOs exhibit an outstanding uranium adsorption efficiency (718 ± 16.6 and 1279 ± 14.5 mg g −1 of m uranium / m PAO in 8 and 32 ppm uranium‐spiked seawater, respectively) among reported hydrogel‐based adsorbents. Most importantly, U‐uptake capacity of this hydrogel can achieve 4.87 ± 0.38 mg g −1 of m uranium / m dry gel just after four weeks within natural seawater. Furthermore, this hydrogel can be massively produced through low‐energy consumption and environmentally‐friendly sunlight polymerization. This work will provide a high‐efficiency and low‐cost adsorbent for massive uranium extraction from seawater.

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Uranium is an extremely abundant resource in seawater that could supply nuclear fuel for over the long-term, but it is tremendously difficult to extract. Here, a new supramolecular poly­(amidoxime) (PAO)-loaded macroporous resin (PLMR) adsorbent has been explored for highly efficient uranium adsorption. Through simply immersing the macroporous resin in the PAO solution, PAOs can be firmly loaded on the surface of the nanopores mainly by hydrophobic interaction, to achieve the as-prepared PLMR. Unlike existing amidoxime-based adsorbents containing many inner minimally effective PAOs, almost all the PAOs of PLMR have high uranium adsorption efficiency because they can form a PAO-layer on the nanopores with molecular-level thickness and ultrahigh specific surface area. As a result, this PLMR has highly efficient uranium adsorbing performance. The uranium adsorption capacity of the PLMR was 157 mg/g (the U PAO in the PLMR was 1039 mg/g), in 32 ppm uranium-spiked seawater for 120 h. Additionally, uranium in 1.0 L 100 ppb U-spiked both water and seawater can be removed quickly and the recovery efficiency can reach 91.1 ± 1.7% and 86.5 ± 1.9%, respectively, after being filtered by a column filled with 200 mg PLMR at 300 mL/min for 24 h. More importantly, after filtering 200 T natural seawater with 200 g PLMR for only 10 days, the uranium-uptake amount of the PLMR reached 2.14 ± 0.21 mg/g, and its average uranium adsorption speed reached 0.214 mg/(g·day) which is very fast among reported amidoxime-based adsorbents. This new adsorbent has great potential to quickly and massively recover uranium from seawater and uranium-containing wastewater. Most importantly, this work will provide a simple but general strategy to greatly enhance the uranium adsorption efficiency of amidoxime-functionalized adsorbents with ultrahigh specific surface area via supramolecular interaction, and even inspire the exploration of other adsorbents.

Although metal–organic frameworks (MOFs) own excellent uranium adsorption capacity but are still difficult to conveniently extract uranium from seawater due to the discrete powder state. In this study, a new MOF-based macroporous membrane has been explored, which can high-efficiently extract uranium through continuously filtering seawater. Through modifying the UiO-66 with poly(amidoxime) (PAO), it can disperse well in a N,N-dimethylformamide solution of graphene oxide and cotton fibers. Then, the as-prepared super-hydrophilic MOF-based macroporous membrane can be fabricated after simple suction filtration. Compared with nonmodified MOFs, this UiO-66@PAO can be dispersed uniformly in the membrane because it can stabilize well in the solution, which have largely enhanced uranium adsorbing capacity owing to the modified PAO. Last but not least, different from powder MOFs, this UiO-66@PAO membrane provides the convenient and continuously uranium adsorbing process. As a consequence, the uranium extraction capacity of this membrane can reach 579 mg·g−1 in 32 ppm U-added simulated seawater for only 24 h. Most importantly, this UiO-66@PAO membrane (100 mg) can remove 80.6% uranyl ions from 5 L seawater after 50 filtering cycles. This study provides a universal method to design and fabricate a new MOF-based adsorbent for high-efficient uranium recovery from seawater.

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Although eco-friendly amidoxime-based adsorbents own an excellent uranium (U)-adsorption capacity, their U-adsorption efficiency is commonly reduced and even damaged by the biological adhesion from bacteria/microorganisms in an aqueous environment. Herein, we present an antibiofouling ultrathin poly­(amidoxime) membrane (AUPM) with highly enhanced U-adsorption performance, through dispersing the quaternized chitosan (Q-CS) and poly­(amidoxime) in a cross-linked sulfonated cellulose nanocrystals (S-CNC) network. The cross-linked S-CNC not only can elevate the hydrophilicity to improve the U-adsorption efficiency of AUPM but also can enhance the mechanical strength to form a self-supporting ultrathin membrane (17.21 MPa, 10 μm thickness). More importantly, this AUPM owns a good antibiofouling property, owing to the broad-spectrum antibacterial quaternary ammonium groups of the Q-CS. As a result, within the 1.00 L of low-concentration (100 ppb) U-added pure water (pH ≈ 5) and seawater (pH ≈ 8) for 48 h, 30 mg of AUPM can recover 93.7% U and 91.4% U, respectively. Furthermore, compared with the U-absorption capacity of a blank membrane without the Q-CS, that of AUPM can significantly increase 37.4% reaching from 6.39 to 8.78 mg/g after being in natural seawater for only 25 d. Additionally, this AUPM can still maintain almost constant tensile strength during 10 cycles of adsorption–desorption, which indicates the relatively long-term usability of AUPM. This AUPM will be a promising candidate for highly efficient and large-scale U-recovery from both U-containing waste freshwater/seawater and natural seawater, which will be greatly helpful to deal with the U-pollution and enrich U for the consumption of nuclear power. More importantly, the work will provide a new convenient but universal strategy to fabricate new highly enhanced low-cost U-adsorbents, through the introduction of both an antibacterial property and a high mechanical performance, which will be a good reference for the design of new highly efficient U-adsorbents.

Dynamic covalent bond-based shape memory polymers (DCB-SMPs) are one of most important SMPs which have a wide potential application prospect. Different from common strong covalent bonds, DCBs own relatively weak bonding energy, similarly to the supramolecular interactions of noncovalent bonds, and can dynamically combine and dissociate these bonds. DCB-SMP solids, which can be designed to respond for different stimuli, can provide excellent self-healing, good reprocessability, and high mechanical performance, because DCBs can obtain dynamic cross-linking without sacrificing ultrahigh fixing rates. Furthermore, besides DCB-SMP solids, DCB-SMP hydrogels with responsiveness to various stimuli also have been developed recently, which have special biocompatible soft/wet states. Particularly, DCB-SMPs can be combined with emerging 3D-printing techniques to design various original shapes and subsequently complex shape recovery. This review has summarized recent research studies about SMPs based on various DCBs including DCB-SMP solids, DCB-SMP hydrogels, and the introduction of new 3D-printing techniques using them. Last but not least, the advantages/disadvantages of different DCB-SMPs have been analyzed via polymeric structures and the future development trends in this field have been predicted.

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