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Abstract: The selective extraction of minor actinides(III) from the lanthanides(III) is a key step for spent fuel reprocessing. Theoretical calculations of geometries, electronic structures, coordination complexion, and thermodynamic properties of the actinides are essential for understanding the separation mechanisms and relevant reactions. This article presents a critical review of theoretical studies on actinide systems involved in the An(III)/Ln(III) separation process. We summarize various theoretical methods for electronic and molecular scale modeling and simulations of actinide coordination systems. The complexing mechanisms between metal cations and organic ligands and the strategies for the design of novel ligands for separation are discussed as well. [Copyright &y& Elsevier]

Abstract: 3-Nitrotyrosine(3-NY) has been reported as a potential source of reactive oxygen species (ROSs). In this work, plasmid pBR322 DNA was irradiated by gamma rays in aqueous solution in presence and absence of 3-NY, DNA strand breaks were analyzed by neutral electrophoresis followed by quantification with image analysis software. It was found that the presence of 3-NY could effectively reduce radiation-induced DNA strand breaks. A side-by-side comparison was performed between 3-NY and tyrosine, the results showed that the protective role 3-NY was comparable with tyrosine, which might imply that protein tyrosine nitration might not significantly decrease its ability as a free radical scavenger. [Copyright &y& Elsevier]

Abstract: Proteins are targets of reactive nitrogen species such as peroxynitrite and nitrogen dioxide. Among the various amino acids in proteins, tyrosine and tryptophan residues are especially susceptible to attack by reactive nitrogen species. On the other hand, protein tyrosine phosphorylation has gained much attention in respect to cellular regulatory events and signal transduction. Peroxynitrite-mediated nitration of peptide YPPPPPW and phosphopeptide pYPPPPPW were studied at pH 7.4. The predominant nitrated products were separated and identified by reverse phase high performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC-MS). The nitration sites were established by tandem electrospray ionization-mass spectrometry (LC-MS/MS). A regulatory effect of tyrosine phosphorylation/dephosphorylation on peptide nitration was observed. YPPPPPW was predominantly nitrated at tyrosine residue while pYPPPPPW was nitrated at tryptophan one. Our results can help in understanding the biochemical significance of the relationship of tyrosine phosphorylation and nitration in proteins. [Copyright &y& Elsevier]

The selective removal and immobilization of uranyl ions from aqueous solutions is essential for the sustainable development of nuclear energy. Herein, a robust lanthanide‐organic framework material (IHEP‐24) is developed for simultaneous fluorescence sensing, selective adsorption, and photocatalytic reduction of uranium, integrating three different functions in one material. The confined space formed by the coordination assembly of viologen derivative ligands and metal‐oxygen clusters can act as precise recognition sites for uranyl, allowing IHEP‐24 to efficiently detect and capture uranyl ions. In addition, the presence of a viologen‐based radical ligand enables IHEP‐24 to a further photocatalytic reduction of the adsorbed uranyl to amorphous UO2. The mechanisms of adsorption and photocatalysis are revealed by batch experiments, photoelectrochemical characterizations, and theoretical calculations. This study provides a reference for the construction of robust multi‐functional MOF materials and also provides support for the deep removal and immobilization of radionuclides from aqueous solution. [ABSTRACT FROM AUTHOR]

Electrospray Ionization Mass Spectrometry (ESI‐MS) technique and density functional theory (DFT) calculations were combined to study the formation of the complexes of lanthanides (Ln = La, Ce, Nd, Sm, Eu, Yb) and actinides (UO22+, Th4+) with CyMe4‐BTBP (6,6′‐bis(5,5,8,8‐tetramethyl‐5,6,7,8‐tetrahydro‐benzo‐[1,2,4‐]triazin‐3‐yl)‐[2,2′]bipyridine) to understand the mechanisms during the extraction process. Mass spectrometry titrations showed the formation of the complexation in acetonitrile. For lanthanides, only 1:2 complexes ([Ln(L)2]3+, [Ln(L)2(CH3CN)]3+), [Ln(L)2(NO3)]2+) were found at low [Ln]/[L] concentration ratios, whereas the 1:1 complexes ([Ln(L)(NO3)2]+) were observed when the [Ln]/[L] concentration ratio reached 1.0. For uranyl complexes, 1:1 complex ([UO2L(NO3)]+) was the only species within the measuring range. Th4+ complexes had two compositions: 1:1 and 1:2, in which 1:2 species was the dominant complex. Collision‐induced dissociation (CID) was employed to characterize the fragmentation process. The fragmentation process was unfolded sequentially on both sides of CyMe4‐BTBP ligand with the loss of alkyl groups and cleavage of triazinyl rings. The CID results of CyMe4‐BTBP complexes revealed a slight difference depending on the metal center. The DFT calculations showed that the stable complexes formed in acetonitrile solution were consistent with the ESI‐MS results. [ABSTRACT FROM AUTHOR]

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+) as charge balancing ions (named U‐Squ‐CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U‐Squ‐CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non‐porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water‐filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single‐crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non‐porous crystalline material. [ABSTRACT FROM AUTHOR]

Metal–organic rotaxane compounds (MORCs) with supramolecular (pseudo)rotaxane motifs as main structures have inherent dynamic character, but their potential as responsive molecular machines is largely hampered by poor responsiveness to external stimuli. In this study, using a multi‐functionalized pseudorotaxane linker that combines two kinds of functionalities, a novel MORC, U‐bpybc‐CB8 (U refers to uranyl, bpybc refers to 1, 1'‐bis(4‐carboxybenzyl)‐4, 4'‐bipyridinium, and CB8 is cucurbit[8]uril), with multi‐responsive capability that can respond to both light and thermal stimuli, is reported. The characterization, combining spectra measurements and single‐crystal X‐ray diffraction, shows that, due to the involvement of viologen‐functionalized flexible organic dicarboxylate guest molecule in the CB8‐ involved pseudorotaxane ligand, the resultant uranyl‐based MORC exhibits photochromic behavior after UV or visible light irradiation. More interestingly, it is revealed that the exceptional thermal response of U‐bpybc‐CB8 as temperature increases from 170 to 270 K, i.e., volume expansion followed by contraction after the inflection temperature of ≈230 K, can be stemmed from the lattice flexibility of this metal–organic supramolecular network. The dual responsiveness of MORCs reported here demonstrates the potential of such supramolecular assemblies as smart molecular components like sensors and switches that respond to light irradiation or temperature changes. [ABSTRACT FROM AUTHOR]

The present paper is dedicated to the quantitative determination of oxygen-containing impurities in the LiF–NaF–KF eutectic using electrochemical (cyclic and square-wave voltammetry) and reduction melting methods. The LiF–NaF–KF melt was analyzed before and after purifying electrolysis. The amount of oxygen-containing impurities removed from the salt during purification was determined. It was found that after electrolysis, the concentration of oxygen-containing impurities decreased by 7 times. The results obtained via electrochemical techniques and reduction melting were well-correlated, which made it possible to evaluate the quality of the LiF–NaF–KF F melt. To verify the analysis conditions, mechanical mixtures of LiF–NaF–KF containing Li2O were analyzed using the reduction melting method. The oxygen concentration in the mixtures varied from 0.672 to 2.554 wt. %. Based on the analysis results, the dependence approximated by the straight line was obtained. These data may be used to draw calibration curves and to further develop the procedure of oxygen analysis of fluoride melts. [ABSTRACT FROM AUTHOR]

A magnetic Metal–Organic Framework (MOF) nanocomposite, namely Cu-BTC@Fe3O4 (BTC = 1,3,5-benzenetricarboxylate) was used for magnetically retrievable separation of uranyl (UO22+) in the presence of competitive ions. A significant adsorption amount of 312 mg/g was achieved for uranium over Cu-BTC@Fe3O4 at a pH value of 4.5. Extended X-ray Absorption Fine Structure (EXAFS) analysis indicated that the interaction of Cu-BTC@Fe3O4 with UO22+ is the synergistic coordination of carboxylate groups of BTC ligand, Fe3O4-COOH, and hydrate H2O for UO22+ ions. In addition to identifying a stable and retrievable adsorbent, the results generally elucidate UO22+ removal of MOFs composites. [ABSTRACT FROM AUTHOR]

The polynuclear metal clusters continually attract wide interest due to their intriguing structures and potential applications in various scientific fields. Here, four actinide clusters have been synthesized by the utilization of multifunctional ligand ferrocenecarboxylic acid (HFcc) and Th4+/U4+ ions by solvent evaporation or solvothermal synthesis strategies in different solvents. Therein, compounds 1, 2 and 4 feature similar [An6(μ3‐O)4(μ3‐OH)4]12+ cores, which are further coordinated by 12 Fcc− ligands and different solvent molecules. The U6Fe12 cluster of compound 4 is linked by four free HFcc molecules via multiple hydrogen bonding to form a supramolecular cluster [U6(μ3‐O)4(μ3‐OH)4(Fcc)12(H2O)4] ⋅ 4HFcc. The cluster core of compound 3 is a μ3‐O2− bridged [U3(μ3‐O)]10+ unit, which is further coordinated by 10 Fcc− ligands via three kinds of coordination modes. It is worth noting that multifunctional Fcc− ligand not only endows compound 1 a main redox wave at E1/2=0.720 V in CH2Cl2/DMF solution, but also enables it to exhibit aggregation‐induced emission (AIE) property. [ABSTRACT FROM AUTHOR]

Review: 387 refs. [ABSTRACT FROM AUTHOR]

Graphical abstract Adsorption/incorporation of the uranyl species with equatorial ligands including the water, hydroxyl, carbonate, bicarbonate ligands on the (1 0 4) surface. Abstract Here we present a combined DFT and molecular dynamics study of uranyl (U(VI)) interaction mechanisms with the calcite (104) surface in aqueous solution. The roles of three anion ligands (CO 3 2−, HCO 3 −, OH−) and solvation effect in U(VI) interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite (1 0 4) surface prefers to exist in molecular state rather than dissociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U(VI) → Ca(II). In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U(VI) → Ca(II), and the one with UO 2 (CO 3) 2 (H 2 O)2− as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilic ability of the (104) surface to different extents, where the UO 2 (CO 3) 3 Ca 2 species contributes to the largest degree of energy changes (−53 kcal/mol). Our calculations proved that the (104) surface also has the ability to immobilize U(VI) via either surface complexing or ion exchange mechanisms under different pH values. [ABSTRACT FROM AUTHOR]

The binary Ga–Al alloy cathode has been proven to be a prospective candidate for the separation of actinides over lanthanides (Lns) in the dry reprocessing. Therefore, in this work the electrochemical behaviors of U(III) on solid Al, liquid Ga and Ga–Al eutectic alloy cathodes were studied by cyclic voltammetry, and the kinetic properties of U(III)/U on these reactive cathodes were also investigated via electrochemical impedance spectroscopy technique in LiCl–KCl melts. The results showed that the exchange current density (j0) of U(III)/U on the Ga–Al eutectic alloy cathode is the largest, and followed the order: Ga–Al eutectic alloy > Ga > Al. Finally, U was electro-separated on the binary Ga–Al eutectic alloy cathode in a molten salt system containing U and representative Lns (La, Ce, Pr, Nd). The electrolysis products were validated to be Al3U and Ga3U according to XRD and SEM–EDS characterizations. The extraction rate of U was determined to be 88.3% via ICP-OES. This work is of theoretical guidance for high-temperature molten salt electro-separation of An over Ln. [ABSTRACT FROM AUTHOR]

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring‐in‐ring(s) system comprising a hydrogen‐bonded macrocycle and cyclobis(paraquat‐o‐phenylene) tetracation (o‐Box) or cyclobis(paraquat‐p‐phenylene) tetracation (CBPQT4+, p‐Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single‐crystal X‐ray diffraction analysis, this ring‐in‐ring(s) system features the box‐directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o‐Box) and H5G (1 a/o‐Box). Remarkably, a dimeric shish‐kebab‐like ring‐in‐rings superstructure H7G2 (1 a/o‐Box) or H8G2 (1 a/p‐Box) is formed from the coaxial stacking of two ring‐in‐rings units. The formation of such unique dimeric superstructures is attributed to the large π‐surface of this 2D planar macrocycle and the conformational variation of both host and guest. [ABSTRACT FROM AUTHOR]

Use of abiotic chemical systems for understanding higher order superstructures is challenging. Here we report a ring‐in‐ring(s) system comprising a hydrogen‐bonded macrocycle and cyclobis(paraquat‐o‐phenylene) tetracation (o‐Box) or cyclobis(paraquat‐p‐phenylene) tetracation (CBPQT4+, p‐Box) that assembles to construct discrete higher order structures with adaptive conformation. As indicated by mass spectrometry, computational modeling, NMR spectroscopy, and single‐crystal X‐ray diffraction analysis, this ring‐in‐ring(s) system features the box‐directed aggregation of multiple macrocycles, leading to generation of several stable species such as H4G (1 a/o‐Box) and H5G (1 a/o‐Box). Remarkably, a dimeric shish‐kebab‐like ring‐in‐rings superstructure H7G2 (1 a/o‐Box) or H8G2 (1 a/p‐Box) is formed from the coaxial stacking of two ring‐in‐rings units. The formation of such unique dimeric superstructures is attributed to the large π‐surface of this 2D planar macrocycle and the conformational variation of both host and guest. [ABSTRACT FROM AUTHOR]

Promoting light absorption range of photocatalysts is of great significance to improve solar light‐driven photocatalytic CO2 reduction efficiency. Herein, a new viologen‐based multicomponent heterotrimetallic metal–organic framework (MOF) [Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb)12][FeIII(CN)6]6 (IHEP‐14) with an unprecedented (6, 18)‐connected she‐d topology is presented. Upon UV irradiation, this MOF undergoes ligand and iron photoreduction, and a single‐crystal‐to‐single‐crystal transformation to generate persistent radical‐containing MOF [Cu3Th6(µ3‐O)4(µ3‐OH)4(cpb•)12][FeII(CN)6]6 (IHEP‐15). This radical‐containing MOF shows excellent stability without fading after at least 2 months in air. Besides extending the photoabsorption to a wider wavelength range covering from 200 to 2,500 nm, the generation of persistent radical in IHEP‐15 also largely enhances its CO2 adsorption capacity by a factor of three due to the strong affinity between π orbital of the radical and the π system of CO2. These attributes endow IHEP‐15 with excellent visible/NIR light‐driven CO2 photoreduction activity, with CO production rates under visible and NIR irradiation of 570.3 and 209.3 µmol h−1 g−1, respectively. Notably, the latter is a record high for NIR‐induced CO production among all MOFs reported so far. [ABSTRACT FROM AUTHOR]

Separation of trivalent actinide (An(III)) and lanthanide (Ln(III)) is a worldwide challenge of nuclear waste treatment. Designing ligands with efficient An(III)/Ln(III) separation performance is still one of the key issues for the disposal of accumulated radioactive waste and the recovery of minor actinides. Recently, N-heterocyclic ligands modified with amide groups have shown excellent An(III)/Ln(III) separation performance. The preorganized structure of the ligands has a great impact on the An(III)/Ln(III) separation performance. We theoretically investigated the extraction behaviors of Am(III) and Eu(III) using phenanthroline (L1 and L2) and bipyridine (L3 and L4) based ligands with a completely or partially preorganized structure. The properties of these ligands and their coordination structures, bonding nature and thermodynamic behaviors with the Am(III) and Eu(III) complexes have been systematically studied in a theoretical fashion. The analyses of the bonding nature suggest that the Am–N bonds possess more covalence than the Eu–N bonds. The thermodynamic results indicate that L2 with a completely preorganized structure has the strongest extraction ability and the best Am(III)/Eu(III) selectivity, while L3 with the most flexible skeleton appears to have the weakest extraction ability and the lowest Am(III)/Eu(III) selectivity. And L1 and L4 have similar performances with regard to Am(III)/Eu(III) selectivity. The results suggest that a certain degree of preorganization of the ligand structure can enhance the extraction ability and Am(III)/Eu(III) selectivity. This work provides valuable information for designing efficient ligands for An(III)/Ln(III) separation by the preorganization strategy. [ABSTRACT FROM AUTHOR]

The coordination chemistry of f‐block elements (lanthanide and actinide) in molten salts has become a resounding topic in view of its great importance to the research and development (R&D) of molten salt reactors and pyroprocessing. In this Review article, a general overview of the coordination chemistry of f‐block elements in molten salts is provided including past achievements and recent advances. Particular emphases are placed on the oxidation state, speciation, and solution structure of f‐block metal ions in molten salts, as well as their relationships with the salt composition. Furthermore, this review briefly discusses the spectroscopic and theoretical methods that complement each other in revealing the coordination properties. [ABSTRACT FROM AUTHOR]

The competition of uranium and vanadium ions is a major challenge in extracting uranium from seawater. In-depth exploration of the complexation of uranium and vanadium ions with promising ligands is essential to design highly efficient ligands for selective recovery of uranium. In this work, we systematically explored the uranyl and vanadium extraction complexes with three tetradentate N,O-mixed donor analogues including the rigid backbone ligands 1,10-phenanthroline-2,9-dicarboxylic acid (PDA, L1) and 5H-cyclopenta[2,1-b:3,4-b′]dipyridine-2,8-dicarboxylate acid (L3), as well as the flexible ligand [2,2′-bipyridine]-6,6′-dicarboxylate acid (L2) using density functional theory (DFT). These ligands coordinate to the uranyl cation in a tetradentate fashion, while L1 and L3 act as tridentate ligands toward VO2+ due to the smaller ionic radius of VO2+ and larger cleft sizes of L1 and L3. Bonding analyses show that the metal–ligand bonding orbitals of the uranyl complexes [UO2L(CO3)]2−, [UO2L(OH)]−, and [UO2L(H2O)] mainly arise from the interactions of the U 5f, 6d orbitals and N, O 2p orbitals. Because of the rigid structure and more suitable chelate ring size, the L1 ligand possesses a stronger complexing ability for uranyl ions than other ligands, while the L3 ligand has weaker binding affinity than L1 and L2. All these ligands prefer to coordinate with the uranyl cation rather than vanadium ion, indicating the selectivity of these ligands to [UO2(CO3)3]4− over H2VO4− and HVO42− in seawater. This is mainly attributed to the metal ion size-based selectivity and structural preorganization of the ligands. These results demonstrate that the backbone of these ligands affect their extraction behaviors. It is expected that this work might prove useful in designing efficient ligands for uranium extraction from seawater. [ABSTRACT FROM AUTHOR]

The fractionation of high-level radioactive waste from nuclear power plants simplifies the handling of its components, and facilitates the reduction of radiotoxic effects on the environment. The search and study of new ligands for solvent extraction, as one of the methods in fractionation, remains a complex and important research task. In this work, four pyridine diphosphonate ligands were synthesized. These ligands are part of the class of the N,O-donor extractants, which are selective towards Am(III). The separation factor SF(Am/Eu) for the best extractant reached values up to 10. The influence of the substituents on the efficiency of extraction and complexation of trivalent f-elements, the kinetics of extraction, and the behavior of the ligand at the interface were described. The effect of nitric acid concentration on the extraction was shown. The stoichiometry of the complexes was determined by slope analysis in solvent extraction experiment and verified by spectrophotometric titration in acetonitrile. Liquid tension experiments with a pendant drop method revealed the interfacial properties of the ligands in "F-3 solvent/H2O" and "F-3 solvent/HNO3" systems. The relationship between the surface activity and the ligand structure was shown. Studies of the extraction kinetics were performed in a modified Lewis cell. The effect of the ligand structure on the extraction rate was shown. The DFT calculation with the B3LYP density functional was used to explain the extraction properties of the ligands, including selectivity. The calculation of the pre-organization energy of the ligands explained the kinetics and extraction patterns for the studied series. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel functionalized ionic liquid was synthesized for the Mo(VI)/U(VI) separation in HNO 3. • The highest SF of Mo(VI) over U(VI) exceeds 104, thus setting a new record for their separation. • Even after five cycles, [BHIB][NTf 2 ] can still extract more than 97 % of Mo(VI). • This work achieves efficient separation of Mo(VI) from U(VI) and is expected to optimize existing processes. We describe here a hydroxyoxime-functionalized ionic liquid, 1-butyl-3-(4-hydroxy-3-((hydroxyimino)methyl)benzyl)-1H-imidazol-3-ium bis((trifluoromethyl)sulfonyl)amide ([BHIB][NTf 2 ]), for the isolation and purification of 99Mo from 235U. This material exhibits remarkable extraction efficiency for Mo(VI) from 0.1 to 2 M HNO 3 and can effectively distinguish Mo(VI) from U(VI). The attained highest separation factor (SF) of Mo(VI) over U(VI) exceeds 104, thus setting a new record for their separation. Additionally, the extracted Mo(VI) can be efficiently recovered using either NH 4 OH or the mixture of NH 4 OH and (NH 4) 2 CO 3. This excellent extraction performance is sustained even after five cycles. The extraction efficiency remains stable following exposure to 150 kGy gamma irradiation, thus providing robust experimental support for potential engineering applications. Slope analysis and EXAFS results indicate that [BHIB][NTf 2 ] forms a 2:1 complex with Mo(VI) during the extraction process primarily driven by a cation exchange mechanism. When one equivalent of Mo(VI) migrates from the aqueous phase to the organic phase, each of two equivalents [BHIB][NTf 2 ] remove one of H+ and migrate to the aqueous phase to maintain charge balance. This investigation introduces a highly efficient and environmentally benign method for separation, alongside providing novel insights into ligand design for the efficacious differentiation of Mo(VI) and U(VI) under HNO 3 conditions, potentially streamlining current methodologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrolytic extraction of rare earths in LiCl-KCl molten salts by co-reduction is an order of magnitude higher than using an active cathode. • The method allows rapid extraction of 99.9 % of cerium in less than 4 h with an actual current efficiency of 97.8 %. The extraction of lanthanides in spent fuel reprocessing plays a key role in the development of nuclear energy. In this work, the extraction of the typical fissionable cerium elements has been studied by electrolytic co-reduction of Al(III) and Ce(III) in LiCl-KCl-CeCl 3 molten salts assisted by KAlCl 4. The electrochemical behavior of the reduction of Al(III) and Ce(III) on a molybdenum electrode was studied by cyclic voltammetry (CV), square wave voltammetry (SWV), and open circuit chronopotentiometry (OCP), and specific peaks of five Al-Ce intermetallic compounds were detected. After 2.7 h of galvanostatic electrolysis at a current density of 0.064 A cm-2, the extraction efficiency and current efficiency of Ce(III) reached 99.9 % and 91.3 % respectively. Potentiostatic electrolysis is slightly more efficient, with 99.9 % Ce(III) extraction in 3.5 h at a current efficiency of 97.8 %. The products of electrolysis are rod-shaped alloys (Al 11 Ce 3 , Al 3 Ce, Al 2 Ce), and the molten salts purified by electrolytic separation are free of impurity signals and can be reused for electrolytic refining. [ABSTRACT FROM AUTHOR]

Theoretical studies demonstrate that the attachment of stronger electron-donating groups enhances the coordination capacity for uranyl ions. [Display omitted] • The extraction behaviors of uranium with six modulated pentadentate ligands have been explored by DFT. • The attachment of stronger electron-donating groups enhances the coordination capacity for uranyl ions. • The H 2 L 3 ligand possesses higher complexation capacity for uranium extraction from seawater. At present, the development of efficient adsorption functional groups is essential for uranium extraction from seawater. In this work, the complexation of uranyl ions with a series of electronically modulated N 3 O 2 -pentadentate planar ligands (H 2 L) has been explored by quantum chemical calculations. All the modified ligands are found to be fully chelated with the uranyl ions, forming the fivefold equatorial coordinated extraction complexes, which indicates that the introduction of substituents has little effect on the coordination of the ligands. The H 2 L 3 ligand with the strong electron-donating methoxy group substituted to ortho-phenol demonstrates stronger covalent bonding toward uranyl ions. Consequently, H 2 L 3 possesses higher complexation capacity than other ligands, which may have potential application in uranium extraction from seawater. Conversely, the substitution on the amino groups seems to be not conducive to increasing the affinity of ligands for uranyl ions, and the complexing capacity of the ligands is reduced for substituents with weaker electron-donating ability. This work gives an insight into the extraction behaviors of different N 3 O 2 -pentadentate derivatives with uranyl ions, and provides a theoretical basis for the design and development of multidentate ligands for seawater uranium recovery. [ABSTRACT FROM AUTHOR]

Four novel uranyl coordination polymers (CPs) have been synthesized by the utilization of viologen derivative ligand, 1,1'‐bis(3,5‐dicarboxyphenyl)‐4,4'‐bipyridinium (H4bdbp ⋅ 2Cl), and uranyl nitrate under hydrothermal reactions through the regulation of different kinds of inorganic acids (HF, HCl, HNO3, HClO4, H2SO4). Compound 1 features a unique triple‐stranded helix structure with a helical pitch of 31.578 Å. The ligands in compounds 2–4 have similar configurations, while their 3D structures are completely different due to the presence of different kinds of anions. The anions play different roles in the frameworks of these uranyl CPs. In addition, compound 2 possesses strong fluorescence both in solid‐state and aqueous suspension‐state. It is demonstrated that compound 2 can selectively detect Fe3+ over several competing metal cations in aqueous solution. [ABSTRACT FROM AUTHOR]

Efficient separation of neptunium and plutonium from spent nuclear fuel is essential for advanced nuclear fuel cycles. At present, the development of effective actinide separation ligands has become a top priority. As common adsorbents for extracting uranium from seawater, amidoxime-based adsorbents may also be able to separate actinides from high-level liquid waste (HLLW). In this work, the complexation of Np(IV , V , VI) and Pu(IV) and alkyl chains (R = C13H26) modified with amidoximate (AO−) and carboxyl (Ac−) functional groups was systematically studied by quantum chemical calculations. For all the studied complexing species, the RAc− and RAO− ligands act as monodentate or bidentate ligands. Complexes with AO− groups show higher covalency of the metal–ligand bonding than the analogues with Ac− groups, in line with the binding energy analysis. Bonding analysis verifies that these amidoxime/carboxyl-based adsorbents possess higher coordination affinity toward Pu(IV) than toward Np(IV), and the Np(VI) complexes have stronger covalent interactions than Np(V). According to thermodynamic analysis, these adsorbents have the ability to separate Np(IV , V , VI) and Pu(IV), and also exhibit potential performance for partitioning Pu(IV) from Np(IV) under acidic conditions. This work can help to deeply understand the interaction between transuranium elements and amidoxime-based adsorbents, and provide a theoretical basis for the separation of actinides with amidoxime-based adsorbents. [ABSTRACT FROM AUTHOR]

We present here the synthesis of a novel fluorescent actinide polyrotaxane compound URCP1 through the utilization of an end‐cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non‐coordinating guest motif in the obtained polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature‐triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature‐triggered structural dynamics in URCP1 represents the first report of actinide polyrotaxane with such feature in solid‐state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4×10−3 ppm. [ABSTRACT FROM AUTHOR]

Herein, we report a new uranyl–organic polyhedron U4L4 (L = BTPCA) assembled from uranyl and a semirigid tritopic ligand. By adjusting the carbon chain length of organic templates, two complexes can be obtained based on the diverse secondary assembly of U4L4 cages. The mechanism of different arrangements of U4L4 cages induced by organic templates was explored in detail. [ABSTRACT FROM AUTHOR]

Mutual separation of trivalent americium (Am3+) and curium (Cm3+) ions through liquid–liquid extraction is challenging due to the similarity in their chemical properties. Three N, O combined extractants 2,6-pyridinedicarboxylic acid di(N-ethyl-4-fluoroanilide) (Et(pFPh)DPA), diphenyl(2-pyridyl)phosphine oxide (Ph2PyPO), and alkyldiamide amine with 2-ethylhexylalkyl chains (ADAAM(EH)) have been identified to exhibit selectivity for Am3+ over Cm3+. In this work, the structures, bonding nature, and thermodynamic behaviors of a series of representative Am- and Cm-complexes with these ligands have been systematically investigated using density functional theory (DFT) calculations. Based on our calculations, the ONO angle formed by three donor atoms of the ligand in the Am-complex is slightly larger than that in its Cm-analogue. The studied ligands show their preference toward Am3+ by opening their "mouths" slightly wider. According to the Mayer bond order and the quantum theory of atoms in molecules (QTAIM) analyses, the interactions between the O donor atoms of these ligands and Am3+ and Cm3+ ions show some weak partial covalent character, and compared to the Am–O bond, there is relatively more covalency in the Cm–O bond in the corresponding complex. However, opposite results can be found in the Am–N and Cm–N bonding for the first two ligands. Particularly, for the better separation ligand ADAAM(EH), the Am–N and Cm–N interactions are extremely weak and no covalent character exists in the bonding. Nevertheless, the difference between the very weak Am–N and Cm–N interactions still leads to a better performance of ADAAM(EH). Based on the comparison of these ligands, we can find that weakening the binding ability of N atoms in the ligand may increase the difference between the Am–N and Cm–N interactions, thus enhancing the Am3+/Cm3+ separation ability of the ligand. Our study might provide new insights into understanding the selectivity of these three N, O combined ligands toward minor actinides and pave the way for designing efficient Am3+/Cm3+ extraction and separation ligands. [ABSTRACT FROM AUTHOR]

• The performance of Ag/AgCl and Pb/PbCl 2 reference electrodes in LiCl-KCl melt was systematically studied. • The stability of reference electrode membrane materials Boron nitride and mullite tubes was compared. • The stability of Boron nitride was poorer than that of mullite tubes. • The fast response of metal–metal ion pairs Ag/AgCl and Pb/PbCl 2 are almost the same. In the pyrochemical reprocessing of spent nuclear fuel (SNFs), a reference electrode with long life and high stability is extremely important for the electrochemical extraction actinides (An). In this work, Ag/AgCl and Pb/PbCl 2 reference electrodes using boron nitride (BN) and mullite tubes as reference electrode membrane materials in LiCl-KCl eutectic melt at different temperature (723 ∼ 773 K) were reported. The stability of reference electrodes immersed in melt for a long time and under electrolysis conditions was systematically studied by different electrochemical methods including cyclic voltammetry (CV), open-circuit chronopotentiometry (OCP) and chronoamperometric (CA). The results showed that BN membrane reference electrodes have excellent ions conductivity and can obtain smooth electrochemical curves. But when it was used for a long time (about 30 h), potential drift would occur. Thus, the stability of the membrane was excellent in short time. On the contrary, the ionic conductivity of mullite membrane reference electrodes was more inferior than that of BN. However, this could be improved as the temperature increased. At the same time, the potential was stable during reference electrodes immersed in melt for 48 h and there was only slight drift (145 h, 80 mV for Ag/AgCl and 40 h, 40 mV for Pb/PbCl 2 reference electrodes) under long-term electrolysis, which shows that mullite membrane reference electrodes have extremely high stability and practical application prospects. [ABSTRACT FROM AUTHOR]

MOF-76 exhibits not only high sensitivity for the detection of U(vi), but also high adsorption capacity of 298 mg g−1 at a low pH value of ∼3.0. Furthermore, the high selectivity for uranium adsorption over a series of competing metal ions is also illustrated. [ABSTRACT FROM AUTHOR]

To evaluate how halogen and actinide atoms affect the electronic structures and bonding nature, we have theoretically investigated a series of the actinide halides An(TRENTIPS)X (An = Th–Pu; X = F–I); several of them have been synthesized by Liddle's group. The An–X bond distances decrease from An = Th to Pu for the same halides, and the harmonic vibrational frequencies for the An–X bonds are more susceptible to being affected by the halogen atoms. The analyses of bonding nature reveal that the An–X bonds have a certain covalency with a polarized character, and the σ-bonding component in the total orbital contribution is greatly larger than the corresponding π-bonding ones based on the analysis of the NOCVs (the natural orbitals for chemical valence). Furthermore, the electronic structures of the thorium complexes are obviously different from those of the uranium and transuranic analogues due to more valence electrons in Th 6d orbitals. In addition, thermodynamic results suggest that the U(TRENTIPS)Br complex is the most stable and U(TRENTIPS)Cl has the highest reactivity based on the halide exchange reaction of U(TRENTIPS)X complexes using Me3SiX. The reduction ability of the tetravalent An(TRENTIPS)X is sensitive to halogen atoms according to the calculated electron affinity of the An(TRENTIPS)X and the reactions An(TRENTIPS)X + K → An(TRENTIPS) + KX. This work presents the effect of the halogen and the actinide atoms on the structures, bonding nature and redox ability of a series of the tetravalent actinide halides with TREN ligand and facilitates our in-depth understanding of f-block elements, which could provide theoretical guidance for experimental work on actinide halides, especially for the synthetic chemistry of transuranic halides. [ABSTRACT FROM AUTHOR]

Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding. [ABSTRACT FROM AUTHOR]

Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding. [ABSTRACT FROM AUTHOR]

A series of point defects in uranium mononitride (UN) have been studied by first-principles DFT+U calculations. The influence of intrinsic defects on the properties of UN was explored by considering the anti-ferromagnetic (AFM) order along the [001] direction. Our results show that all the point defects lead to obvious volume swelling of UN crystal. Energetically, the interstitial nitrogen defect is the most favorable one among single-point defects in UN crystal with the formation energy of 4.539 eV, while the N-Frenkel pair becomes the most preferable one among double-point defects. The AFM order induces obvious electron spin polarization of uranium towards neighboring uranium atoms with opposite spin orientations in UN crystal. [ABSTRACT FROM AUTHOR]

Elastic metal–organic materials (MOMs) capable of multiple stimuli‐responsiveness based on dual‐stress and thermally responsive triple‐helix coordination polymers are presented. The strong metal‐coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Å stacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time. Crystal structure analyses at different temperatures reveal that this thermoresponsiveness is achieved by adaptive regulation of the triple‐helix chains by fine‐tuning the opening angle of flexible V‐shaped organic linkers and rotation of its lateral conjugated groups to resist possible expansion, thus demonstrating the vital role of adaptive reorganization of triple‐helix metal–organic chains as a molecular spring‐like motif in crystal jumping. [ABSTRACT FROM AUTHOR]

Elastic metal–organic materials (MOMs) capable of multiple stimuli‐responsiveness based on dual‐stress and thermally responsive triple‐helix coordination polymers are presented. The strong metal‐coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Å stacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time. Crystal structure analyses at different temperatures reveal that this thermoresponsiveness is achieved by adaptive regulation of the triple‐helix chains by fine‐tuning the opening angle of flexible V‐shaped organic linkers and rotation of its lateral conjugated groups to resist possible expansion, thus demonstrating the vital role of adaptive reorganization of triple‐helix metal–organic chains as a molecular spring‐like motif in crystal jumping. [ABSTRACT FROM AUTHOR]

Herein we present a new viologen‐based radical‐containing metal–organic framework (RMOF) Gd‐IHEP‐7, which upon heating in air undergoes a single‐crystal‐to‐single‐crystal transformation to generate Gd‐IHEP‐8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical‐radical interactions, and their long‐lifetime radicals result in wide spectral absorption in the range 200–2500 nm. Gd‐IHEP‐7 and Gd‐IHEP‐8 show excellent activity toward solar‐driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h−1 g−1, respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd‐IHEP‐8 versus Gd‐IHEP‐7 is attributed to intermediates stabilized by enhanced hydrogen bonding. [ABSTRACT FROM AUTHOR]

We modeled the solution behavior of zirconium in uranium dioxide (UO2) by using density functional theory. The Coulomb repulsion of uranium 5f elections was characterized by a spherically averaged Hubbard parameter. Our results indicate that zirconium prefers to locate at U vacancies in UO2 and presents a slight tendency to accumulate in thermodynamics. The solution energies for hcp Zr metal and monoclinic ZrO2 indicates that these two precipitates are insoluble in UO2. In perfect UO2, the band-gap opening is governed by U 5f peaks around the Fermi energy, whereas the solution of zirconium further leads to the band gap splitting owing to the introduction of zirconium 4d peaks especially at high defect concentrations. [ABSTRACT FROM AUTHOR]

Phenanthroline based ligands have shown potential performance for partitioning trivalent actinides from lanthanides. In this work, we have explored four ester and amide ligands based on the phenanthroline skeleton and elucidated the separation mechanism between Am(III) and Eu(III) ions. The molecular geometries and extraction reactions of the metal–ligand complexes were modeled by using scalar-relativistic density functional theory. The results show that the amide based ligands have stronger coordination ability with the metal ions than the corresponding ester based ligands. According to the thermodynamic results, ligands N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (L2) and N,N′-(1,10-phenanthroline-2,9-diyl)bis(N-ethyl-P-methyl-N-(p-tolyl)phosphinic amide) (L4) appear to have the strongest complexing ability, which is supported by the result of electrostatic potential (ESP) and the M–OL bond orders. Moreover, ligand L2 has excellent selectivity for Am(III)/Eu(III) among the four ligands. Additionally, the bonding properties between the metal ions and the ligands reveal that the Am(III)/Eu(III) selectivity stems from the Am–N bonds with more covalent character, which is supported by the analysis of the hardness of the ligands and the bond orders. This work provides useful information for understanding the Am(III)/Eu(III) selectivity of phenanthroline derived ligands bearing ester and amide groups. [ABSTRACT FROM AUTHOR]

Two novel thorium-based organic frameworks (Th-IHEP-5 and Th-IHEP-6) were assembled from a hexanuclear thorium cluster, porphyrin derivative ligand and linear carboxylic acid ligands via a mixed-ligand strategy. As a stable heterogeneous catalyst, Th-IHEP-5 exhibited high photocatalytic activity for the oxidation of 2-chloroethyl ethyl sulfide (CEES) and the fixation of CO2. The good catalytic effect is attributed to the large conjugated system of porphyrin and the photosensitizer enhancing effects of bipyridine. [ABSTRACT FROM AUTHOR]

Separation of adjacent actinides (An) americium and curium is a critical and challenging step in advanced nuclear fuel cycles. Herein, we performed a quantum chemical calculation to explore the separation behavior of Am(III) from Cm(III) by two representative amide-type ligands, N,N′-dimethyl-N,N′-dioctyl-2-(2-hexyloxyethyl)malonamide (DMDOHEMA) and N,N,N′,N′,N″,N″-hexaalkyl-nitrilotriacetamide (NTAamide). It was found that the better energy match of Am 5f orbitals and O, N 2p orbitals of the amide-type ligands resulted in the selective ability of these ligands to Am3+ over Cm3+. Complexation reaction analysis predicted that An(DMDOHEMA)2(NO3)3 and [An(NTAamide)2]3+ were the most probable species in the separation processes. [ABSTRACT FROM AUTHOR]

Two phosphorylated cyclohexapeptides (CPs) bearing one (CP1) or two phosphates (CP2) were synthesized to explore the interactions between uranyl ions and very small cyclic peptides. According to the results of the ESI–MS and fluorescence titrations, the 1:1 uranyl-CPs complexes are the main products with the affinity constants of 7.3 × 104 and 2.0 × 105 for CP1 and CP2, respectively. Density functional theory calculations indicate phosphoryl and carboxyl groups coordinate uranyl in mono-dentate and bi-dentate fashions due to steric effects, which is consistent with the results of extended X-ray absorption fine structure spectroscopy. [ABSTRACT FROM AUTHOR]

Both Al and Ga have exhibited excellent performance, respectively, for the An/Ln separation based on molten salt electrolysis, and the Al-Ga composite cathode may have superior properties. Therefore, in this work, the electrochemical behaviors of Ce (III) on the binary Al-Ga electrode were systematically explored by co-reduction of Ce (III), Al (III) and Ga (III) on a W electrode. A new oxidation signal of Al 2 Ga 2 Ce ternary intermetallic compound was successfully detected. In addition, for comparison, the co-reduction behaviors of Ce (III) with Al (III) and Ce (III) with Ga (III) on an inert tungsten electrode were also investigated. The results showed that different kinds of alloys are formed on the surface of W electrode. Finally, several typical Ga-Ce and Al-Ga-Ce intermetallic compounds were obtained by potentiostatic electrolysis and the deposited products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). [ABSTRACT FROM AUTHOR]

• MXene-derived hierarchical titanate nanostructures (HTNs) were prepared by a mild in situ chemical conversion method. • HTNs can efficiently remove Eu(III) with large adsorption capacities (more than 200 mg/g). • The ion-exchange behavior of Eu(III) with Na+ or K+ was confirmed. • The exchanged Eu(III) ions were confined in the nanoscale interlayers of HTNs and then immobilized. Developing versatile materials that rapidly and efficiently adsorb radionuclides is an urgent objective for environmental remediation in response to radioactive contamination. Herein, we report the preparation of hierarchical titanate nanostructures (HTNs) by a in situ chemical conversion strategy using a two-dimensional MXene crystal precursor. These HTNs are very stable and can efficiently remove Eu(III) with large sorption capacities, owing to well-maintained layered structures and abundantly exchangeable guest cations. The replacement of sodium or potassium ions with Eu(III) in HTN interlayers has been confirmed by X-ray diffraction (XRD), photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). The extended X-ray sorption fine structure (EXAFS) results, in combination with density functional theory (DFT) calculations, further indicate that the sequestration of Eu(III) is realized by forming inner-sphere surface complexes in nano-confined space, evidenced by the decrease of Eu-O distances (R) and coordination numbers (N). The finding of the inner-sphere complexation induced by Ti−O/Ti−OH coordination and confinement effect provides new insights into the interaction mechanism between radionuclides and titanates. Given their extraordinary sorption capacity and facile synthesis under mild conditions, these HTNs are promising candidates for the efficient removal of trivalent lanthanides and actinides from aqueous solutions during the cleanup of radioactive pollution in the environment. [ABSTRACT FROM AUTHOR]

As a less explored avenue, actinide‐based metal‐organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate‐based anionic MOF supported by uranyl–carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain‐type building unit is reported for the first time in uranyl‐based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly‐synthesized anionic material has been used to remove Eu3+ ions, as a non‐radioactive surrogate of Am3+ ion, through an ion‐exchange process with [(CH3)2NH2]+ ions in its open channels, as evidenced by a combination of 1H NMR spectroscopy, EDS and PXRD. [ABSTRACT FROM AUTHOR]

Theoretical studies demonstrated that P350 is a promising extractant for separation of neptunium and plutonium. [Display omitted] • The complexation behaviors of Np(IV,V,VI) and Pu(IV) with three neutral phosphate ligands were explored by DFT. • These phosphate ligands have the ability to Pu(IV)/Np(IV) and Np(VI)/Np(V) separation. • The complexing ability of P350 is stronger than TBP and TiAP. • P350 is the more promising extractant for separation of Np and Pu in nitric acid solution. Effective treatment of the transuranic neptunium and plutonium from nuclear waste is of great importance and remains a challenge for developing advanced nuclear fuel cycles. Currently, novel ligands for efficient separation of actinides need to be designed urgently. Neutral extractants containing phosphorus have shown great potential for actinides separation. In this paper, we systematically explored the extraction and separation performances of neptunium(IV,V,VI) and plutonium(IV) by three phosphorus derivatives, di(1-methyl-heptyl) methyl phosphonate (P350), tri- iso -amyl phosphate (TiAP), and tributyl phosphate (TBP) by density functional theory (DFT). The outcomes showed that these neutral phosphorus reagents act as monodentate ligands through the P O group for all the extraction complexes. According to bonding nature analysis, the P350 ligand has the strongest complexing ability to the studied actinide cations. In addition, these ligands show a preference to coordination with Pu4+ and NpO 2 2+ over Np4+ and NpO 2 +, respectively. As expected, the thermodynamic analysis demonstrated the potential application of these neutral extractants in Np and Pu separation, among which the P350 ligand is more promising than TBP and TiAP in acid solution system. This work can help to further understand the separation mechanism of Np/Pu with neutral phosphorus reagents and provide insight into the development of highly efficient extractants in recovery of Np and Pu. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations reveal that adjusting N-, O-donor affinity enhances Am/Eu separation ability of the ligands. [Display omitted] • Am(III), Eu(III) Back-extraction reaction free energy with three disulfonated diamide N-heterocyclic ligands were well modeled by using density functional theory. • The bonds between Am(III) ions and N donor atoms in studied ligands are partial covalence interactions and three disulfonated diamide N-heterocyclic ligands have preference back-extraction ability toward Am(III). • Disulfonated diamide N-heterocyclic ligands' Am(III) preference can be modified by adjusting its N- and O- atoms' affinity. Separation of minor actinides (MAs) from lanthanides (Ln) is a vital and challenging stage in advanced nuclear waste treatment. Development of water-soluble back-extraction ligand is regarded as a feasible alternative method for high efficiency An(III)/Ln(III) separation. Therefore, theoretical investigating on the deep mechanism behind the selective back-extraction of An(III) is very important. In this work, Am- and Eu-complexes with three water-soluble disulfonated N-heterocyclic ligands, disulfonated N,N'-diphenyl-2,9-diamide-1,10-phenanthroline (DS-Ph-DaPhen, L 1), disulfonated N,N'-diphenyl-2,9-diamide-2,2′-Dipyridine (DS-Ph-DADipy, L 2), and disulfonated N,N'-diphenyl-2,9-diamide 5H-cyclopenta[2,1-b:3,4-b']-Dipyridine (DS-Ph-Da-5H-Cyclo-PentaDipy, L 3) were systematically investigated using quasi-relativistic density functional theory (DFT) method. Electrostaic potential (ESP) and restrained electroStatic potential (RESP) atomic charge on donor atoms indicate that N atoms' affinity toward metal ions in L 2 and L 3 was increased by replaceing the phenanthroline ring with dipyridine ring and 5H-Cyclo-PentaDipyridine ring, while the affinity of O atoms seem to decrease from L 1 to L 2 and L 3. Through Wiberg bond indices and quantum theory of atoms in molecule (QTAIM) analyses, three ligands' Am(III) preference may be attributed to the weak but different extend partial covalency in Am-N and Eu-N bonds. Based on the NBO population and PDOS analyses, slightly more overlap of Am-5 f and N/O-2 p orbitals than those between Eu-4 f and N/O-2 p orbitals. Based on the theoretical calculation, the covalency difference between Am-N and Eu-N bonds seems to have inverse correlation with the intensity of M−N bonds. However, all the theoretical results suggest that, by increasing N's affinity and weakening O' affinity at the same time, ligand's Am(III)/Eu(III) separation ability can be improved. This work offers some useful information for changing ligands' An(III)/Ln(III) back-extraction and separation abilities by adjusting the affinity of donor N and O atoms in its central N-heterocyclic skeleton, and may shed light for future designing of more efficient An(III)/Ln(III) back-extraction ligands. [ABSTRACT FROM AUTHOR]

The cathodic collection efficiency (CCE) for the exhaustive electrolysis of uranium is very low; however, determination of the mechanism responsible for this phenomenon has been hindered by the lack of information about the uranium species present in molten salts. Herein, we used in situ X-ray absorption spectroscopy and quasi in situ electronic absorption spectroscopy to study the chemical speciation of uranium during the electrolysis process. For the first time, uranium was revealed to be continuously converted between [UCl 6 ]2− and [UCl 6 ]3−, leading to problematic cyclic electrolysis. This cyclic electrolysis process was the main cause of the low CCE during exhaustive electrolysis, and also hindered the full recovery of uranium. To eliminate this cyclic electrolysis process, we adopted a sacrificial active lanthanum metal anode. The lanthanum metal dissolved at the anode to form La3+ ions, which hindered the conversion between [UCl 6 ]2− and [UCl 6 ]3−. Thus, the uranium cycle between the cathode and the anode was eliminated, resulting in a significant improvement in the CCE for exhaustive electrolysis. • In situ X-ray absorption spectroscopy and quasi in situ electronic absorption spectroscopy were used to study the chemical speciation of uranium during the electrolysis process. • Continuously converting between UIII and UIV leads to a cyclic electrolysis of U. • An active anode was adopted, and the uranium cycle between the cathode and the anode was eliminated, resulting in a significant improvement in the current efficiency for exhaustive electrolysis. [ABSTRACT FROM AUTHOR]

We studied geometric and electronic structures as well as thermodynamic properties of complexes [M(CyMe4-BTBP)2(NO3)]2+ and [M(CyMe4-BTBP)2]3+ with M = Am(III), Cm(III) and Ln(III) (La-Lu) theoretically. The actinide-nitrogen bonding is principally ionic with higher covalency in An-N bonds than in the Ln-N analogues. The selectivity towards An(III) over Ln(III) (La, Ce, Pr, Pm, Sm, Eu and Yb) is influenced by formed complexes to different extents by comparison of changes of Gibbs free energy of reaction, ΔΔGAm/Ln, for formation of [AmL2]3+/[LnL2]3+, [AmL2(NO3)]2+/[LnL2(NO3)]2+, and [AmL2(NO3)]2+/[LnL2]3+. The Am(III) selectivity is enhanced for [AmL2(NO3)]2+/[LnL2]3+ over [AmL2]3+/[LnL2]3+. [ABSTRACT FROM AUTHOR]

Uranyl–organic frameworks (UOFs) have recently been the object of many research endeavors due to the unique coordination mode of uranyl ions and their attractive physicochemical properties. Here, a new (3,4)‐connected UOF (U‐IHEP‐4) assembled from uranyl and porphyrin ligand tetrakis(4‐carboxyphenyl)porphyrin (H4TCPP) is reported, which represents the first case of actinide porphyrinic MOFs. Adsorption experiments in DMF solution demonstrated that U‐IHEP‐4 selectively adsorbs positively charged dyes, which is in line with its negatively charged framework and large pore volume ratio (90 %). Remarkably, U‐IHEP‐4 exhibited high catalytic activity for the dehydrogenation of N‐heterocycles to synthesize the corresponding aromatic heterocycles and it can be used as an efficient heterogeneous catalyst. A new uranyl–organic framework (U‐IHEP‐4) based on porphyrin derivative ligand was synthesized, filling the gap of porphyrinic MOFs in the field of actinide chemistry. The compound U‐IHEP‐4 was demonstrated to be a heterogeneous catalyst for dehydrogenation of N‐heterocycles. [ABSTRACT FROM AUTHOR]