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Harnessing solar energy by photocatalytically converting oxygen and water into high-value-added H2O2 is a promising way of alleviating both environmental and energy issues. It is worth noting that suppressing detrimental side reactions, such as the generation of •O2−, is a critical approach to enhancing H2O2 production. Herein, a 2-fold interpenetrating 3D uranium-organic framework (YTU-W-1) was developed and introduced for photocatalytic H2O2 production. The material demonstrates a different photocatalytic mechanism when employing uranyl as an initiator, as compared with the conventional semiconductor photocatalytic pathway involving photo-generated charge carriers. Benefiting from the strong hydrogen abstraction effect of the U≡O• and the direct one-step oxygen reduction pathway, YTU-W-1 exhibits enhanced photocatalytic performance for H2O2 production with yield efficiency of 221 µmol h−1 g−1. Furthermore, YTU-W-1 displays a high H2O2 selectivity of 68%, confirmed by rotating ring-disk electrode (RRDE) measurement. DFT calculations were used to elucidate the critical role of uranyl in the photocatalytic oxygen reduction reaction for H2O2 production. This research introduces an innovative approach to photo driven H2O2 production, underscoring the potential for heterogeneous catalysts to engage in photocatalytic reactions independently of photo-generated charge carriers. [ABSTRACT FROM AUTHOR]

The development of adsorbent materials for effective capture of radioactive iodomethane (CH3I) from the off-gas of used nuclear fuel reprocessing, remains a significant and challenging line of research because currently state-of-art adsorbents still suffer from low binding affinity with CH3I. Here, we proposed a brand-new adsorption topological structure by developing a 2D interdigitated layered framework, named SCU-20, featuring slide-like channel with multiple active sites for CH3I capture. The responsive rotating-adaptive aperture of SCU-20 enables the optimal utilization of all active sites within the pore for highly selective recognition and capture of CH3I. A record-breaking CH3I uptake capacity of 1.84 g/g was achieved under static sorption conditions with saturated CH3I vapor. Both experimental and theoretical findings demonstrated that the exceptional uptake of SCU-20 towards CH3I can be attributed to the confined physical electrostatic adsorption of F sites, coupled with the chemical nitrogen methylation reaction with uncoordinated N atoms of pyrazine. Moreover, dynamic CH3I uptake capacity potentially allows for the capture of CH3I in simulated real-world off gas reprocessing conditions. This study highlights the potential of SCU-20 as a promising candidate for efficient capture of iodine species and contributes to the development of effective solutions for radioactive iodine remediation. [ABSTRACT FROM AUTHOR]

Post-synthetic functionalization of covalent organic frameworks (COFs) is an alternative way to enhance and broaden their properties and potential applications. However, the chemical functionalization of COFs is a great challenge because traditional procedures are often time- and energy-consuming, while the crystallinity of COFs can be damaged under harsh conditions. Here we report the in-situ introduction of functional graft chains onto the skeleton of COFs during the synthesis process through the combination of radiation-induced synthesis and graft polymerization techniques under 60Co gamma-ray radiation. The synthesis and functionalization of COFs are simultaneously accomplished in a chemical system under ambient conditions yielding a large number of different functionalized COFs. The obtained carboxyl-functionalized COFs exhibit excellent radioactive uranium removal capabilities from aqueous solution with fast uptake dynamics, high adsorption capacity, and excellent selectivity over other competing metal ions. [ABSTRACT FROM AUTHOR]

Partitioning of americium from lanthanides (Ln) present in used nuclear fuel plays a key role in the sustainable development of nuclear energy1–3. This task is extremely challenging because thermodynamically stable Am(III) and Ln(III) ions have nearly identical ionic radii and coordination chemistry. Oxidization of Am(III) to Am(VI) produces AmO22+ ions distinct with Ln(III) ions, which has the potential to facilitate separations in principle. However, the rapid reduction of Am(VI) back to Am(III) by radiolysis products and organic reagents required for the traditional separation protocols including solvent and solid extractions hampers practical redox-based separations. Herein, we report a nanoscale polyoxometalate (POM) cluster with a vacancy site compatible with the selective coordination of hexavalent actinides (238U, 237Np, 242Pu and 243Am) over trivalent lanthanides in nitric acid media. To our knowledge, this cluster is the most stable Am(VI) species in aqueous media observed so far. Ultrafiltration-based separation of nanoscale Am(VI)-POM clusters from hydrated lanthanide ions by commercially available, fine-pored membranes enables the development of a once-through americium/lanthanide separation strategy that is highly efficient and rapid, does not involve any organic components and requires minimal energy input.A new strategy to separate radioactive americium from lanthanides based on complexation with polyoxometalates and ultrafiltration technique is highly efficient and rapid, does not involve any organic components and requires minimal energy input. [ABSTRACT FROM AUTHOR]

Efficient removal of iodide (I−) and iodate (IO3−) from aqueous solution is highly desirable for waste disposal and remediation of radioiodine contamination. We report here a bifunctional anion exchange resin Purolite A530E for the effective I−/IO3− adsorption, which shows a priority anion-exchange affinity for I− (99%) over IO3− (9.7%). The maximum adsorption capacity for I− is 275.16 mg·g−1 fitted by the Langmuir isotherm model, much higher than most adsorbents. Furthermore, Purolite A530E exhibits great selectivity for I− over competing anions, which endows the resin with promising I− remediation that over 99% I− can be removed from simulated Hanford groundwater (HGW). [ABSTRACT FROM AUTHOR]

Platinum recovery from waste electrical and electronic equipment (WEEE) in highly acidic solutions is significant to the electronics industry and environmental remediation. However, the lack of ingenious design and synergetic coordination gives rise to unsatisfied PtCl42− extraction capacities and selectivities in most previously reported adsorbents (e.g., polymeric and inorganic materials). Herein, we proposed a synergistic strategy that realizes highly selective PtCl42− uptake through first- and second-sphere coordinations. The proof-of-concept imine-linked covalent organic framework (SCU-COF-3) was found to chelate PtCl42−via the direct N⋯Pt coordination and the synergistically interlaminar N—H⋯Cl hydrogen bonds, which was disclosed by the comprehensive analysis of extended X-ray adsorption fine structure (EXAFS) characterizations and density functional theory (DFT) calculations. The unique adsorption mechanism imparts a superior adsorption capacity (168.4 mg g−1) and extraordinary Pt(II) selectivity to SCU-COF-3 under static conditions. In addition, SCU-COF-3 exhibits an upgraded distribution coefficient of 1.62 × 105 mL g−1, one order of magnitude higher than those of reported natural adsorbents. Specifically, SCU-COF-3 can extract PtCl42− quantitatively from a simulated acidic waste solution coexisting with other 12 competitive ions, suggesting its promising application in practical scenarios. [ABSTRACT FROM AUTHOR]

Uranium nitrides play important roles in dinitrogen activation and functionalization and in chemistry for nuclear fuels, but the synthesis and isolation of the highly reactive uranium(VI) nitrides remains challenging. Here, we report an example of transition metal (TM) stabilized U(VI) nitride complexes, which are generated by the photolysis of azide-bridged U(IV)-TM (TM = Rh, Ir) precursors. The U(V) nitride intermediates with bridged azide ligands are isolated successfully by careful control of the irradiation time, suggesting that the photolysis of azide-bridged U(IV)-TM precursors is a stepwise process. The presence of two U(VI) nitrides stabilized by three TMs is clearly demonstrated by an X-ray crystallographic study. These TM stabilized U(V) nitride intermediates and U(VI) nitride products exhibit excellent stability both in the solid-state and in THF solution under ambient light. Density functional theory calculations show that the photolysis necessary to break the N-N bond of the azide ligands implies excitation from uranium f-orbital to the lowest unoccupied molecular orbital (LUMO), as suggested by the strong antibonding N-(N2) character present in the latter. The synthesis and isolation of uranium(VI) nitride complexes remains challenging. Here, the authors report an example of transition metal (TM) stabilized U(VI) nitride complexes, generated via photolysis of azide-bridged U(IV)-TM precursors. [ABSTRACT FROM AUTHOR]

Open metal site (OMS) seated in a luminescent lanthanide (Ln) metal center offers an opportunity for rationally tuning the spectroscopic behavior of lanthanide-organic frameworks aiming for a wide range of sensing applications. However, given the spherical nature of common coordination geometries of trivalent lanthanides and the generally strong Ln-O bonds, the lanthanide based OMS is rarely reported and difficult to be functionalized. We report here a unique europium-organic framework containing abundant quasi-OMS that is protected by an abnormal weak Eu-O bond. These quasi-OMSs offer reversible direct binding sites for water molecules probed by X-ray crystallography, leading to sensitive, visible, and ratiometric luminescent sensing toward humidity and water content in organic solvents. The specific recognition of water based on quasi-luminescent-OMSs gives rise to a superior water detection limit down to 0.0003% v/v, which is one order of magnitude lower than that of Karl Fischer method. [ABSTRACT FROM AUTHOR]

99Tc is a long-lived radionuclide present in large amounts as TcO4- anion in used nuclear fuel. Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process. Despite the progress achieved in the past few years, the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition, is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process. However, their design philosophy remains elusive, with challenges coming from charge repulsion, steric hindrance, and insufficient reactive sites within the materials. Herein, we present a design philosophy of cationic polymer network materials for TcO4- separation by systematic precursor screening and structure prediction. This affords an optimized material, SCU-CPN-2 (SCU=Soochow University), with extremely high positive charge density while maintaining high radiation resistance. SCU-CPN-2 exhibits a record high adsorption capacity (1,467 mg/g towards the surrogate ReO4-) compared to all anion-exchange materials reported up to date. In addition to ultrafast adsorption kinetics, SCU-CPN-2 has remarkable selectivity over nitrate and sulfate, and facile recyclability. [ABSTRACT FROM AUTHOR]