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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.

Nuclear accidents and the improper disposal of nuclear wastes have led to serious environmental radioactive pollutions. The rational design of adsorbents for the highly efficient separation of strontium(II) is essential in treating nuclear waste and recovering radioactive strontium resources. Metal–organic frameworks (MOFs) are potential materials for the separation of aqueous metal ions owing to their designable structure and tunable functionality. Herein, a novel 3D MOF material MOF‐18Cr6, in which 1D channels are formed using 18‐crown‐6‐ether‐containing ligands as channel walls, is fabricated for strontium(II) separation. In contrast to traditional MOFs designed by grafting functional groups in the framework pores, MOF‐18Cr6 possesses regular 18‐crown‐6‐ether cavities on the channel walls, which not only can transport and intake strontium(II) via the channels, but also prevent blockage of the channels after the binding of strontium(II). Consequently, the functional sites are fully utilized to achieve a high strontium(II) removal rate of 99.73 % in simulated nuclear wastewater. This study fabricates a highly promising adsorbent for the separation of aqueous radioactive strontium(II), and more importantly, can provide a new strategy for the rational design of high‐performance MOF adsorbents for separating target substances from complex aqueous environments. [ABSTRACT FROM AUTHOR]

As the power‐conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long‐term ambient stability. Here, the application of PCN‐224 quantum dots (QDs) is reported, a typical Zr‐based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN‐224 QDs with abundant Lewis‐base groups (e.g., CO, C−N, CN) contribute to high‐quality perovskite films with enlarged grain size and reduced defect density by interaction with under‐coordinated Pb2+. Meanwhile, PCN‐224 QDs enable the well‐matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN‐224 QDs‐treated HTL can capture Li+ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li‐TFSI. Moreover, PCN‐224 QDs mitigated Li+ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs. [ABSTRACT FROM AUTHOR]

An adaptive coordination structure is vital for selective uranium extraction from seawater. By strategy of molecular imprinting, uranyl is introduced into a multivariate metal–organic framework (MOF) during the synthesis process to guide the in situ construction of proper nanocage structure for targeting uranyl binding. Except for the coordination between uranium with four oxygen from the materials, the axial oxygen of uranyl also forms hydrogen bonds with hydrogen from the phenolic hydroxyl group, which enhances the binding affinity of the material to uranyl. Attributing to the high binding affinity, the adsorbent shows high uranium binding selectivity to uranyl against not only the interfering metal ions, but also the carbonate group that coordinates with uranyl to form [UO2(CO)3]4− in seawater. In natural seawater, the adsorbent realizes a high uranium adsorption capacity of 7.35 mg g−1, together with an 18.38 times higher selectivity to vanadium. [ABSTRACT FROM AUTHOR]

UiO‐66‐NH2/black phosphorus quantum dots (MOF/BPQDs) heterojunctions are anchored on the carboxyl cellulose nanofiber (CNF) aerogel with high porosity (>98%) to fabricate high‐efficiency uranium adsorbents (BP@CNF‐MOF). CNF aerogels possess abundant carboxyl groups, which can serve as nucleation centers to in situ synthesize UiO‐66‐NH2 with smaller crystal size, high mass loading, and good adhesion. BP@CNF‐MOF demonstrates good mechanical flexibility and minimal MOF loss from the CNF aerogel, both of which result from the mutual physical interactions and entanglements of CNFs as well as strong binding interactions between MOF crystals and CNF aerogel. Owing to the excellent heterogeneous photocatalytic activity of MOF/BPQDs, on one hand, marine bacteria can be effectively destroyed by reactive oxygen species (ROS). On the other hand, the photocatalytic U(VI) reduction to insoluble U(IV) could be facilitated, thereby allowing more binding sites on the MOF crystals for further U(VI) adsorption. Consequently, compared with dark conditions, the adsorption efficiency of the light irradiated BP@CNF‐MOF increases by 55.3%, reaching up to 6.77 mg‐U per g‐Ads after 6 weeks of exposure to natural seawater. The intrinsic instability of BPQDs can be overcome by MOF coating layer simultaneously. The strategy applied in this work could also be applicable to other superior MOF crystals. [ABSTRACT FROM AUTHOR]

Biology has evolved excellent spatial structures for high‐selectivity and high‐affinity capture of heavy metals. Inspired by the spatial structure of the superb‐uranyl binding protein SUP, we mimic the spatial structure of SUP in metal–organic frameworks (MOFs). The MOF UiO‐66‐3C4N fabricated by introducing 4‐aminoisophthalic acid into UiO‐66 shows high uranyl adsorption capacity both in simulated seawater and in natural seawater. In natural seawater, UiO‐66‐3C4N exhibits 17.03 times higher uranium extraction capacity than that of vanadium, indicating the high selectivity of the adsorbent. The EXAFS analysis and DFT calculation reveal that UiO‐66‐3C4N forms smaller nano‐pocket for uranyl capture than that of SUP protein, which can both restrict the entrance of the other interfering ions with larger size and reinforce the binding by increasing the coordination interaction, and therefore qualify the nano‐pocket with high affinity and high selectivity to uranyl. [ABSTRACT FROM AUTHOR]

[Display omitted] • The incorporation of TCPP(Ni) enhances the visible light absorption of UIO-type MOF. • TCPP(Ni) ligands give rise to the downward LUMO energy level of Zr-oxo cluster. • More mesoporous created by TCPP(Ni) increase utilization of hidden binding sites. • A high U-sorption capacity of 8.95 mg-U/g-Ads is achieved from natural seawater. Integrating multi-functionality into metal–organic frameworks (MOFs) has attracted growing attention as it plays a critical role in realizing the potential of MOFs for a wide variety of applications. Owing to the ultrahigh surface areas and porosity, MOFs have been recognized as potential adsorbents for uranium capture through chemical chelation of uranyl ions (UO 2 2+). As a new type of photocatalyst, however, these MOFs are rarely applied in uranium recovery by photocatalytic reduction of soluble U(VI) to the less soluble U(IV), which is largely due to the limited visible light harvesting as well as the poor separation and transfer of photo-generated carriers. Herein, we present a facile one pot synthetic route to incorporate photo-responsive Ni(II)-centered porphyrin (TCPP(Ni)) ligands into UIO-66-NH 2 (TCPP(Ni) ⊂ MOF) while maintaining the crystal structure and ultrahigh chemical stability. TCPP(Ni) not only provides strong visible light harvesting but also improves the charge transfer from excited ligands to Zr-oxo clusters. Consequently, the mixed-linker strategy boosts the photoreduction of soluble U(VI) to the less soluble U(IV) for uranium immobilization. After optimization, TCPP(Ni) ⊂ MOF-3 presents excellent selective uranium capture from wastewater and natural seawater through combined complexation and photoreduction. Strikingly, after immersing in natural seawater for 25 days, a high uranium sorption capacity of 8.95 ± 0.39 mg-U/g-Ads can be achieved together with good antibacterial ability. This work provides a promising strategy to improve the photoreduction potential of MOF adsorbents for uranium capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • MOF-bonded carbon sponge is designed for photothermally enhancing U(VI) adsorption. • The mass loading of UiO-66-NH 2 prepared by in-situ growth can reach up to 85 wt%. • The monolithic MOF adsorbent exhibits favorable elastic and recyclable performance. • The selectivity of U(VI) can be improved when exposure to light irradiation. • Light irradiation yields a 32.37% increase in the U(VI) adsorption amount than dark. Extraction of radioactive uranium from the natural seawater is regarded as one of the most promising ways to address the shortage of uranium resources. As a kind of potential uranium adsorbent, more attention has been paid to metal–organic framework materials (MOFs) due to large specific surface area and high ion selectivity. Currently, however, MOF adsorbents are hardly applied to the real seawater in view of the relatively low uranium adsorption capacity and recyclable issues. Herein, we present the monolithic MOF adsorbent with photothermally enhancing uranium adsorption capacity. Carbon sponge (CS) substrate with macroporous open cell structure was used as excellent photothermal conversion material. Zr-MOF (UiO-66-NH 2) crystals were in situ grown on the fibrils network of polydopamine (PDA) pre-coated CS to obtain UiO-66-NH 2 @CS-PDA adsorbent. It is found that UiO-66-NH 2 coating with perfect coverage and good adhesion has a high mass loading (>85 wt%). As a result, UiO-66-NH 2 @CS-PDA adsorbents exhibited the advantage of high-selectivity, high-affinity and cycling stability. Compared with the dark condition, the uranium adsorption amount was increased by 32.37% after 4 weeks in the natural seawater under simulated solar irradiation, which was mainly ascribed to the endothermic behavior of uranium adsorption process. Moreover, the elasticity attribute of CS was essential for sustenance of volume variation buffering during seawater flow. As a recyclable and favorable elastic large-scale monolithic MOF adsorbent, UiO-66-NH 2 @CS-PDA holds great promise for extracting uranium from the natural seawater. [ABSTRACT FROM AUTHOR]