Solvent-Dependent Synthesis of Porous Anionic Uranyl-Organic Frameworks Featuring a Highly Symmetrical (3,4)-Connected ctn or bor Topology for Selective Dye Adsorption

A UOF based on a cyclotriphosphazene skeleton: fluorescence sensing of different substituted aldehydes and NACs

A novel uranyl organic framework (U-hdpcp) based on flexible cyclic triphosphazene polycarboxylate ligands was prepared, which possesses the ability to sense aromatic aldehyde solutions (benzaldehyde, salicylaldehyde and 2-bromobenzaldehyde) and nitro compounds (2,4,6-trinitrophenol, 2,4-dinitrophenol and o-nitrophenol). A fluorescent thin film based on U-hdpcp@PVA with the ability to sense aldehyde vapors was prepared via a spin coating method. The work expands the library of UOF materials based on large-sized carboxylic acid ligands and demonstrates promising applications in the field of fluorescent sensors.

Energy-structure-property relationships in uranium metal-organic frameworks

Located at the foot of the periodic table, uranium is a relatively underexplored element possessing rich chemistry. In addition to its high relevance to nuclear power, uranium shows promise for small molecule activation and photocatalysis, among many other powerful functions. Researchers have used metal-organic frameworks (MOFs) to harness uranium's properties, and in their quest to do so, have discovered remarkable structures and unique properties unobserved in traditional transition metal MOFs. More recently, (e.g. the last 8-10 years), theoretical calculations of framework energetics have supplemented structure-property studies in uranium MOFs (U-MOFs). In this Perspective, we summarize how these budding energy-structure-property relationships in U-MOFs enable a deeper understanding of chemical phenomena, enlarge chemical space, and elevate the field to targeted, rather than exploratory, discovery. Importantly, this Perspective encourages interdisciplinary connections between experimentalists and theorists by demonstrating how these collaborations have elevated the entire U-MOF field.

Three-Dimensional Crystalline Covalent Triazine Frameworks via a Polycondensation Approach

The growth of crystalline covalent triazine frameworks (CTFs) is still considered as a great challenge due to the less reversible covalent bonds of triazine linkages. The research studies of crystalline CTFs to date have been limited to two-dimensional (2D) structures, and the three-dimensional (3D) crystalline CTFs have never been reported before. Herein we report the design and synthesis of two 3D crystalline CTFs, termed 3D CTF-TPM and 3D CTF-TPA through a reversible/irreversible polycondensation approach. The targeted 3D CTFs adopt ctn topology, and show moderate crystallinity, relatively large surface area (ca. 2000 m²  g^-1 ), and high CO₂ uptake capacity (23.61 wt.%). Moreover, these 3D CTFs exhibit ultrastability in the presence of boiling water, strong acid (1 M HCl) and strong base (1 M NaOH). This contribution represents the first report of 3D crystalline CTFs, which not only extends their structural diversity but also offers a synthetic strategy and structural basis for expanding practical applications of CTF materials.

State-of-the-art progress for the selective crystallization of actinides, synthesis of actinide compounds and their functionalization

Crystallization and immobilization of actinides to form actinide compounds are of significant importance for the extraction and reutilization of nuclear waste in the nuclear industry. In this paper, the state-of-art progress in the crystallization of actinides are summarized, as well as the main functionalization of the actinide compounds, i.e., as adsorbents for heavy metal ions and organic pollutant in waste management, as (photo)catalysts for organic degradation and conversion, including degradation of organic dyes and antibiotics, dehydrogenation of N-heterocycles, CO₂ cycloaddition, selective alcohol oxidation and selective oxidation of sulfides. This review will give a comprehensive summary about the synthesis and application exploration of solid actinide crystalline salts and actinide-based metal organic frameworks in the past decades. Finally, the future perspectives and challenges are proposed in the end to give a promising direction for future investigation.

Contrasting Networks and Entanglements in Uranyl Ion Complexes with Adipic and trans,trans-Muconic Acids

Adipic (hexane-1,6-dicarboxylic, adpH₂) and trans,trans-muconic (trans,trans-hexa-2,4-diene-1,6-dicarboxylic, mucH₂) acids have been reacted with uranyl cations under solvo-hydrothermal conditions, yielding nine homo- or heterometallic complexes displaying in their crystal structure the effects of the different flexibility of the ligands. The complexes [PPh₄]₂[(UO₂)₂(adp)₃] (1) and [Ni(bipy)₃][(UO₂)₂(muc)₃]·5H₂O (2), where bipy is 2,2'-bipyridine, crystallize as diperiodic networks with the hcb topology, the layers being strongly puckered or quasiplanar, respectively. Whereas [(UO₂)₂(adp)₃Ni(cyclam)]·2H₂O (3), where cyclam is 1,4,8,11-tetraazacyclotetradecane, crystallizes as a diperiodic network, [(UO₂)₂(muc)₃Ni(cyclam)]·2H₂O (4) is a triperiodic framework in which the Ni^II cations are introduced as pillars within a uranyl-muc^2- framework with the mog topology. [UO₂(adp)(HCOO)₂Cu(R,S-Me₆cyclam)]·2H₂O (5), where R,S-Me₆cyclam is 7(R),14(S)-5,5,7,12,12,14-hexamethylcyclam, is a diperiodic assembly with the sql topology, and it crystallizes together with [H₂NMe₂]₂[(UO₂)₂(adp)₃] (6), a highly corrugated hcb network with a square-wave profile, which displays 3-fold parallel interpenetration. In contrast, [(UO₂)₃(muc)₂(O)₂Cu(R,S-Me₆cyclam)] (7) is a diperiodic assembly containing hexanuclear, μ₃-oxido-bridged secondary building units which are the nodes of a network with the hxl topology. The two related complexes [PPh₃Me]₂[(UO₂)₂(adp)₃]·4H₂O (8) and [PPh₃Me]₂[(UO₂)₂(muc)₃]·H₂O (9) crystallize as hcb networks, but their different shapes, undulated or quasiplanar, respectively, result in different entanglements, 2-fold parallel interpenetration in 8 and 2-fold inclined 2D → 3D polycatenation in 9.

Identification of a metastable uranium metal–organic framework isomer through non-equilibrium synthesis

Since the structure of supramolecular isomers determines their performance, rational synthesis of a specific isomer hinges on understanding the energetic relationships between isomeric possibilities. To this end, we have systematically interrogated a pair of uranium-based metal–organic framework topological isomers both synthetically and through density functional theory (DFT) energetic calculations. Although synthetic and energetic data initially appeared to mismatch, we assigned this phenomenon to the appearance of a metastable isomer, driven by levers defined by Le Châtelier's principle. Identifying the relationship between structure and energetics in this study reveals how non-equilibrium synthetic conditions can be used as a strategy to target metastable MOFs. Additionally, this study demonstrates how defined MOF design rules may enable access to products within the energetic phase space which are more complex than conventional binary (e.g., kinetic vs. thermodynamic) products.

Identifying the relationship between structure and energetics in a uranium MOF isomer system reveals how non-equilibrium synthetic conditions can be used as a strategy to target metastable MOFs.

Varied role of organic carboxylate dizwitterions and anionic donors in mixed-ligand uranyl ion coordination polymers

Two organic dizwitterions were combined with various anionic donors to generate a series of five uranyl ion complexes crystallizing as mono- or diperiodic coordination polymers, with separation into two distinct networks in one case.

Mixed-Ligand Uranyl Squarate Coordination Polymers: Structure Regulation and Redox Activity

The electron-rich squarate ion (C₄O₄^2-, SA^2-) possesses electronic delocalization over the entire molecule and good redox activity, and the functionalization of metal-organic complexes with the SA^2- group is desirable. In this work, a mixed-ligand method is used to construct novel uranyl squarate coordination polymers utilizing 4,4'-bipyridine (bpy), 4,4'-bipyridine-N,N'-dioxide (bpydo), 1,10-phenanthroline (phen), 4,4'-vinylenedipyridine (vidpy), and in situ formed oxalate (OA^2-) as ancillary ligands. Seven mixed-ligand uranyl compounds, [(UO₂)(OH)(SA)](Hbpy) (1), [(UO₂)(H₂O)(SA)₂](H₂bpy) (2), (UO₂)(H₂O)(SA)(bpydo)·2H₂O (3), (UO₂)(H₂O)(SA)(phen)·H₂O (4), (UO₂)(OH)(SA)_0.5(phen)·H₂O (5), [(UO₂)(SA)(OA)_0.5](Hphen) (6), and [(UO₂)(SA)(OA)_0.5](Hvidpy) (7), with varying crystal structures were synthesized under hydrothermal conditions. Compound 1, together with bpy molecules filling in the interlayer space as template agents, has a two-dimensional (2D) network structure, while 2 gives a one-dimensional (1D) chain based on mononuclear uranium units. Compound 3 shows a neutral 2D network through the combined linkage of SA^2- and bpydo. Both 4 and 5 have a similar chain-like structure due to the capping effect of phen motifs, while phen molecules in 6 act as templating agents after protonation. Similar to 6, compound 7 has a "sandwich-like" structure in which the Hvidpy motifs locate in the voids of layers of 2D uranyl-squarate networks. The redox properties of typical mixed-ligand uranyl-squarate compounds, 1, 4, and 5 with high phase purity, are characterized using cyclic voltammetry. All three of these uranyl coordination compounds show anode peaks (E_a) at 0.777, 0.804, and 0.760 V, respectively, which correspond to the oxidation process of SA^2- → SA. Meanwhile, cathodic peaks (E_c) at -0.328, -0.315, and -0.323 V corresponding to the reduction process of U(VI) → U(V) are also observed. The results reveal that all three of these uranyl coordination compounds show good redox activity and, most importantly, the interplay between two different redox-active motifs of SA^2- organic linker and uranyl node. This work enriches the library of redox-active uranyl compounds and provides a feasible mixed-ligand method for regulating the synthesis of functional actinide compounds.

Zn(II)/Cd(II)-Based Metal-Organic Frameworks as Bifunctional Materials for Dye Scavenging and Catalysis of Fructose/Glucose to 5-Hydroxymethylfurfural

Functional neutral metal-organic frameworks (MOFs) {[M(5OH-IP)(L)]}_n [M = Zn(II) for ADES-4; Cd(II) for ADES-5; 5OH-IP = 5-hydroxyisophthalate; L = (E)-N'-(pyridin-3-ylmethylene)nicotinohydrazide) have been synthesized by a diffusion/conventional reflux/mechanochemical method and characterized by various analytical techniques. Crystals were harvested by a diffusion method, and single-crystal X-ray diffraction (SXRD) analysis revealed that an adjacent [M₂(COO)₂]_n ladder chain generates isostructural two-dimensional network motifs by doubly pillaring via L. The bulk-phase purity of ADES-4 and ADES-5 synthesized by a versatile synthetic approach has been recognized by the decent match of powder X-ray diffraction patterns with the simulated one. Both ADES-4 and ADES-5 showed selective adsorption of cationic dyes methylene blue (MB), methyl violet (MV), and rhodamine B (RhB) over anionic dye methyl orange (MO) from water with good uptake and rapid adsorption. Utilization of ADES-4 as a chromatographic column filler for adsorptive removal of individual cationic dyes as well as a mixture of dyes has been demonstrated from the aqueous phase. Interestingly, ADES-4 is reusable with good stability, and it showed a dye desorption phenomenon in methanol. The probable mechanism of cationic dye removal based on insight from structural information and plausible supramolecular interactions has also been explored. Both MOFs also showed efficient catalytic transformation of fructose and glucose into the high-value chemical intermediate 5-hydroxymethylfurfural of industrial significance.

3D Uranyl Organic Frameworks Supported by Rigid Octadentate Carboxylate Ligand: Synthesis, Structure Diversity, and Luminescence Properties

Seven three dimensional (3D) uranyl organic frameworks (UOFs), formulated as [NH₄ ][(UO₂ )₃ (HTTDS)(H₂ O)] (1), [(UO₂ )₄ (HTTDS)₂ ](HIM)₆ (2, IM=imidazole), [(UO₂ )₄ (TTDS)(H₂ O)₂ (Phen)₂ ] (3, Phen=1,10-phenanthroline), [Zn(H₂ O)₄ ]_0.5 [(UO₂ )₃ (HTTDS)(H₂ O)₄ ] (4), and {(UO₂ )₂ [Zn(H₂ O)₃ ]₂ (TTDS)} (5), {Zn(UO₂ )₂ (H₂ O)(Dib)_0.5 (HDib)(HTTDS)} (6, Dib=1,4-di(1H-imidazol-1-yl)benzene) and [Na]{(UO₂ )₄ [Cu₃ (u₃ -OH)(H₂ O)₇ ](TTDS)₂ } (7) have been hydrothermally prepared using a rigid octadentate carboxylate ligand, tetrakis(3,5-dicarboxyphenyl)silicon(H₈ TTDS). These UOFs have different 3D self-assembled structures as a function of co-ligands, structure-directing agents and transition metals. The structure of 1 has an infinite ribbon formed by the UO₇ pentagonal bipyramid bridged by carboxylate groups. With further introduction of auxiliary N-donor ligands, different structure of 2 and 3 are formed, in 2 the imidazole serves as space filler, while in 3 the Phen are bound to [UO₂ ]²⁺ units as co-ligands. The second metal centers were introduced in the syntheses of 4-7, and in all cases, they are part of the final structures, either as a counterion (4) or as a component of framework (5-7). Interesting, in 7, a rare polyoxometalate [Cu₃ (μ₃ -OH)O₇ (O₂ CR)₄ ] cluster was found in the structure. It acts as an inorganic building unit together with the dimer [(UO₂ )₂ (O₂ CR)₄ ] unit. Those uranyl carboxylates were sufficiently determined by single crystal X-ray diffraction, and their topological structures and luminescence properties were analyzed in detail.

Controlling the secondary assembly of porous anionic uranyl-organic polyhedra through organic cationic templates

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.

Recent advances in metal-organic frameworks as adsorbent materials for hazardous dye molecules

Water is vital for the sustenance of all forms of life. Hence, water pollution is a universal crisis for the survival for all forms of life and a hurdle in sustainable development. Textile industry is one of the anthropogenic activities that severely pollutes water bodies. Inefficient dyeing processes result in thousands of tons of synthetic dyes being dumped in water bodies every year. Therefore, the efficient removal of synthetic dyes from wastewater has become a challenging research field. Owing to their tuneable structure-property aspects, metal-organic frameworks (MOFs) have emerged as promising adsorbents for the adsorptive removal of dyes from wastewater and textile effluents. In this perspective, we highlight recent studies involving the application of MOFs for the adsorptive removal of hazardous dye molecules. We also classify the developed MOFs into cationic, anionic, and neutral framework categories to comprehend their suitability for the removal of a given class of dyes.

Construction of Hybrid Bimetallic Uranyl Compounds Based on a Preassembled Terpyridine Metalloligand

Six hybrid uranyl-transition metal compounds [UO₂ Ni(cptpy)₂ (HCOO)₂ (DMF)(H₂ O)] (1), [UO₂ Ni(cptpy)₂ (BTPA)₂ ] (2), [UO₂ Fe(cptpy)₂ (HCOO)₂ (DMF)(H₂ O)] (3), [UO₂ Fe(cptpy)₂ (BTPA)₂ ] (4), [UO₂ Co(cptpy)₂ (HCOO)₂ (DMF)(H₂ O)] (5), and [UO₂ Co(cptpy)₂ (BTPA)₂ ] (6), based on bifunctional ligand 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine (Hcptpy) are reported (H₂ BTPA = 4,4'-biphenyldicarboxylic acid). Single-crystal XRD revealed that all six compounds feature similar metalloligands, which consist of two cptpy^- anions and one transition metal cation. The metalloligand M(cptpy)₂ can be considered to be an extended linear dicarboxylic ligand with length of 22.12 Å. Compounds 1, 3, and 5 are isomers, and all of them feature 1D chain structures. The adjacent 1D chains are connected together by hydrogen bonds and π-π interactions to form a 3D porous structure, which is filled with solvent molecules and can be exchanged with I₂ . Compounds 2, 4, and 6 are also isomers, and all of them feature 2D honeycomb (6,3) networks with hexagonal units of dimensions 41.91×26.89 Å, which are the largest among uranyl compounds with honeycomb networks. The large aperture allows two sets of equivalent networks to be entangled together to result in a 2D+2D→3D polycatenated framework. Remarkably, these uranyl compounds exhibit high catalytic activity for cycloaddition of carbon dioxide. Moreover, the geometric and electronic structures of compounds 1 and 2 are systematically discussed on the basis of DFT calculations.

Actinyl-Carboxylate Complexes [AnO2(COOH) n (H2O) m ]2-n (An = U, Np, Pu, and Am; n = 1-3; m = 0, 2, 4; 2n + m = 6): Electronic Structures, Interaction Features, and the Potential to Adsorbents toward Cs Ion

Organic compounds of actinyls and their bonding features have attracted extensive attention in nuclear waste separation due to their characteristics of separating fission products. Herein, detailed studies on the binding sites of [AnO2(COOH) n (H2O) m ]2-n (An = U, Np, Pu, and Am; n = 1-3; m = 0, 2, 4; 2n + m = 6) complexes toward Cs are predicted by calculation, and their electronic excitation characteristics were illustrated, providing theoretical supports for the design of Cs adsorbents. The quantum theory of atom in molecules and electron localization function have been implemented to analyze the chemical bonding characterization. The covalent character of An-OC bonds become weaker with increasing COOH- ligands, and the covalent interaction in An-OC bonds is more obvious than that in An-OH bonds. Total and partial population density of state suggest that the 2p orbits of O have more significant contribution in the low-energy region atoms and the 6d/5f orbits of An have more significant contribution in the high-energy region. The Cs+ best adsorption site on [UO2(COOH)2(H2O)2] and [UO2(COOH)3]- is the adjacent oxalates, and the [UO2(COOH)3]- complexes have better adsorption capacity. Besides, the electronic excitation characteristics of Cs+ adsorption on the UO2(COOH)2(H2O)2 complex were analyzed by the UV-vis spectrum and hole-electron distribution.

Auxiliary Ligand-Dependent Adaptive Regulation of Uranyl Coordination in Mixed-Ligand Uranyl Compounds of Flexible Biphenyltetracarboxylic Acid

The mixed-ligand strategy is one of the important methods for preparing new materials and regulating the properties of materials. In this work, by introducing different auxiliary ligands (ALs), we have obtained a series of mixed-ligand uranyl complexes (1-6) from a flexible biphenyltetracarboxylic acid (H₄bptc) with an adjustable orthogonal conformation and studied the influence of different organic base molecules on the coordination and assembly of H₄bptc with a uranyl cation. It is found that the coordinated ALs, including 4,4'-bipyridine-1,1'-dioxide and 1,10-phenanthroline, partially occupy the coordination sites of the uranyl center and directly affect the molecular conformations and uranyl coordination of flexible bptc linkers. On the other hand, noncoordinated ALs such as protonated 4,4'-bipyridine ([H₂(4,4'-bpy)]²⁺) or dimethylammonium, which work as counterions in the form of encapsulated guests or hydrogen-bonded templates, also have a nonnegligible impact on the conformation and coordination of bptc linkers. Most interestingly, the AL-mediated evolution of uranyl coordination by the bptc linker and coordination geometry of the uranyl center is clearly observed, which suggests the adaptability of flexible bptc linkers to take suitable molecular configurations and uranyl coordination modes so as to adapt to the external regulator agents and varying environment. The physicochemical characterization of these uranyl compounds, especially photoluminescence, is addressed and discussed, and the results reveal that compound 5 has the potential to serve as a multifunctional radiation detection material for UV light and X-ray radiation.

Variability of Uranyl Carboxylates from Rigid Terophenyldicarboxylic Acid Ligands

Three uranyl carboxylates, namely, (UO₂)(L¹)(H₂O)_0.5 (1), [(UO₂)(L²)(H₂O)]·2H₂O (2), and [(UO₂)(L²)(H₂O)]·(CH₃CN) (3), were synthesized hydrothermally from 2',3',5',6'-tetramethyl-(1,1':4',1″-terphenyl)-4,4″-dicarboxylic acid (H₂L¹) and 2',5'-dimethyl-(1,1':4',1″-terphenyl)-3,3″-dicarboxylic acid (H₂L²), which are all steric carboxylic acid ligands but vary with the carboxylic acid group position and methyl group number. It is found that compound 1 displays a three-dimensional 8-fold-interpenetrated net with channels running along the c direction. Compounds 2 and 3 are isostructural, and all display two-dimensional-layered crystal structures but contain different guest molecules. The photophysical measurements reveal that compounds 1 and 2, which contain disordered water molecules, are luminescence-quenched, whereas compound 3 containing acetonitrile molecules is luminescent.

A series of four novel alkaline earth metal-organic frameworks constructed of Ca(ii), Sr(ii), Ba(ii) ions and tetrahedral MTB linker: structural diversity, stability study and low/high-pressure gas adsorption properties

A series of four novel microporous alkaline earth metal–organic frameworks (AE-MOFs) containing methanetetrabenzoate linker (MTB) with composition {[Ca₄(μ₈-MTB)₂]·2DMF·4H₂O}_n (UPJS-6), {[Ca₄(μ₄-O)(μ₈-MTB)_3/2(H₂O)₄]·4DMF·4H₂O}_n (UPJS-7), {[Sr₃(μ₇-MTB)_3/2]·4DMF·7H₂O}_n (UPJS-8) and {[Ba₃(μ₇-MTB)_3/2(H₂O)₆]·2DMF·4H₂O}_n (UPJS-9) (UPJS = University of Pavol Jozef Safarik) have been successfully prepared and characterized. The framework stability and thermal robustness of prepared materials were investigated using thermogravimetric analysis (TGA) and high-energy powder X-ray diffraction (HE-PXRD). MOFs were tested as adsorbents for different gases at various pressures and temperatures. Nitrogen and argon adsorption showed that the activated samples have moderate BET surface areas: 103 m² g⁻¹ (N₂)/126 m² g⁻¹ (Ar) for UPJS-7′′, 320 m² g⁻¹ (N₂)/358 m² g⁻¹ (Ar) for UPJS-9′′ and UPJS-8′′ adsorbs only a limited amount of N₂ and Ar. It should be noted that all prepared compounds adsorb carbon dioxide with storage capacities ranging from 3.9 to 2.4 wt% at 20 °C and 1 atm, and 16.4–13.5 wt% at 30 °C and 20 bar. Methane adsorption isotherms show no adsorption at low pressures and with increasing pressure the storage capacity increases to 4.0–2.9 wt% of CH₄ at 30 °C and 20 bar. Compounds displayed the highest hydrogen uptake of 3.7–1.8 wt% at −196 °C and 800 Torr among MTB containing MOFs.

Four novel microporous alkaline earth metal–organic frameworks (AE-MOFs) containing methanetetrabenzoate linker (MTB): UPJS-6, UPJS-7, UPJS-8 and UPJS-9 have been successfully prepared, characterized and tested as adsorbents for different gases.

Uranyl Ion Complexes of Polycarboxylates: Steps towards Isolated Photoactive Cavities

Consideration of the extensive family of known uranyl ion complexes of polycarboxylate ligands shows that there are quite numerous examples of crystalline solids containing capsular, closed oligomeric species with the potential for use as selective heterogeneous photo-oxidation catalysts. None of them have yet been assessed for this purpose, and some have obvious deficiencies, although related framework species have been shown to have the necessary luminescence, porosity and, to some degree, selectivity. Aspects of ligand design and complex composition necessary for the synthesis of uranyl ion cages with appropriate luminescence and chemical properties for use in selective photo-oxidation catalysis have been analysed in relation to the characteristics of known capsules.

Hydrothermal synthesis of two 2D uranyl coordination polymers: structure, luminescence, and photocatalytic degradation of rhodamine B

Two hydrothermal synthesized uranyl-organic coordination polymers showing effective photocatalytic activities for RhB degradation with quick equilibrium time in water.

Occurrence of polyoxouranium motifs in uranyl organic networks constructed by using silicon-centered carboxylate linkers: structures, spectroscopy and computation

Four polyoxouranium-based uranyl carboxylates have been synthesized based on silicon-centered carboxylate linkers. Oligomerization of the uranyl units from tetrameric unit, to octameric motif and ultimately infinite polyoxouranium chain was observed.

Structural Diversity of Bipyridinium-Based Uranyl Coordination Polymers: Synthesis, Characterization, and Ion-Exchange Application

As well-known functional groups with excellent electro/photochromic and ion-exchange properties, bipyridinium motifs have been used in functionalized metal-organic coordination polymers, but they are still rarely applied to construct actinide coordination polymers. In this work, we utilized a bipyridinium-based carboxylic acid, 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium bis(chloride) ([H₂bcbp]Cl₂), as the organic ligand to assemble with uranyl cations. By the introduction of different kinds of auxiliary ligands and adjustment of the pH, five novel uranyl coordination compounds, 1-5, have been synthesized through hydrothermal reactions. Starting from uranyl ions and terephthalic acid (H₂TP) and H₂bcbp ligands, [(UO₂)₂(bcbp)(TP)₂]·3H₂O (1) has a wave-shaped two-dimensional (2D) structure consisting of dinuclear units connected by terephthalate linkers and further supported by the longer H₂bcbp ligands. [(UO₂)₂(bcbp)(PA)₂]·4H₂O (2) has a zigzag chain of dimeric uranium units, and [(UO₂)₂(bcbp)(bpdc)₂]·5H₂O (3) forms a one-dimensional ribbonlike structure. The 2D structures of [(UO₂)(bcbp)(OH)(H₂O)]·Cl (4) and [(UO₂)(bcbp)Cl]·Cl (5) are similar, both of which are constructed from dinuclear uranyl units and bcbp^2- ligands. Furthermore, the performance for perrhenate removal of compound 4 with a cationic framework is assessed, and we found that compound 4 can efficiently remove ReO₄^- from an aqueous solution in a wide range of pH values. This work extends the library of viologen derivative-based uranyl coordination polymers, provides to some extent broader insights into actinide coordination chemistry of functionalized ligands, and may facilitate the ion-exchange applications of related coordination polymers.

Fabrication of blue organic light-emitting diodes from novel uranium complexes: synthesis, characterization, and electroluminescence studies of uranium anthracene-9-carboxylate complexes

In this study, three uranium(vi) complexes, [UO2(C15H9O2)2(CH3CH2OH)2]·2CH3CH2OH (1), [U2O4(C15H9O2)2(CH3O)2(CH3OH)2]·2CH3OH (2), and [U2O4(C15H9O2)4(CH3OH)2]·2H2O (3), were prepared by reacting anthracene-9-carboxylic acid with uranyl acetate dihydrate using various ligand to uranyl acetate ratios in different solvents. The infrared and UV-Vis spectra along with elemental and thermal analyses showed the formation of mono- and dinuclear anthracene-9-carboxylate complexes of uranium. A 1 to 3 molar ratio of uranyl acetate to anthracene-9-carboxylic acid in ethanol resulted in the formation of the mononuclear complex 1, whereas a 1 to 2 and 1 to 3 molar ratio of uranyl acetate to anthracene-9-carboxylic acid in methanol produced the dinuclear complexes 2 and 3, respectively. Single-crystal structure determinations of 1, 2 and 3 revealed hexagonal bipyramidal geometries for the mononuclear uranium complex of 1 and a pentagonal geometry for the dinuclear uranium complexes of 2 and 3. The single-crystal structures of complexes 2 and 3 showed π-π interactions in contrast to complex 1. The strong π-π interactions in complex 2 and 3 lead to an enhanced photoluminescence intensity in comparison with 1 without π-π interaction. The optical properties of the prepared complexes are associated with the ligand-induced resonant system. The fluorescent uranium complex 1 that showed a blue emission upon excitation at 270 nm was used for the fabrication of a blue organic light-emitting diode (BOLED), an industrially important OLED, using a simple solution-process fabrication method.

In situ nitroso formation induced structural diversity of uranyl coordination polymers

This work presents three possible pathways that could exist in the in situ reaction system. Structural analysis of these compounds revealed that the introduction of nitroso group exerted significant influences on the conformations of ligands, skeletons and 3D structures.

Assembly of porphyrin-based uranium organic frameworks with (3,4)-connected pto and tbo topologies

(3,4)-Connected uranyl–organic frameworks (UOFs) with pto and tbo topologies were constructed via the utilization of triangular [(UO₂)(COO)₃]⁻ as the 3-connected node and square organic linker tetrakis(4-carboxyphenyl)porphyrin (H₄TCPP) as the 4-connected node.

Bimetallic Uranyl Organic Frameworks Supported by Transition-Metal-Ion-Based Metalloligand Motifs: Synthesis, Structure Diversity, and Luminescence Properties

A bifunctional ligand, 2,2'-bipyridine-4,4'-dicarboxylic acid (H₂bpdc), has been used in the investigation of constructing bimetallic uranyl organic frameworks (UOFs). Seven novel uranyl-transition metal bimetallic coordination polymers, [(UO₂)Zn(bpdc)₂] _n (1), [Cd(UO₂)(bpdc)₂(H₂O)₂·2H₂O] _n (2), [Cu(UO₂)(bpdc)(SO₄)(H₂O)₃·2H₂O] _n (3), [CuCl(UO₂)(bpdc)(Hbpdc)(H₂O)₂·H₂O] _n (4), [Cu(UO₂)(bpdc)₂(H₂O)] _n (5), [Co₂(UO₂)₃(bpdc)₆] _n (6), and [Co₃(UO₂)₄(bpdc)₈(Hbpdc)(H₂O)₂] _n (7), have been successfully constructed through the assembly of various transition-metal salts, uranyl ions, and H₂bpdc ligands under hydrothermal conditions. UOFs 1, 5, 6, and 7 adopt three-dimensional (3D) frameworks with different architectures; UOFs 2 and 3 exhibit two-dimensional (2D) wavelike and stairlike layers, respectively, while UOF 4 is a one-dimensional (1D) chain assembly. These UOFs include a wide range of dimensionalities (1D-3D), interpenetrated frameworks, and cation-cation interaction species, suggesting that anion-dependent structure regulation based on the metalloligand [M(bpdc) _m] ^n- motifs, the coordination modes of the metal centers and bpdc^2- ligands, along with the reaction temperature, has a remarkable influence on the formation of bimetallic UOFs, which could be a representative system for the structural modulation of UOFs with various dimensionalities and structures. Furthermore, the thermal stability and luminescent properties of compounds 1, 3, and 6 are also investigated.

Fluorescent sensing and selective adsorption properties of metal-organic frameworks with mixed tricarboxylate and 1H-imidazol-4-yl-containing ligands

Herein, two metal-organic frameworks (MOFs), [Co₄(μ₃-OH)₂(L)(BTB)₂(H₂O)₃]·5.6H₂O (1) and [Cd₃(L)₂(BTB)₂(μ₂-H₂O)]·7.4H₂O (2), based on 1,3-di(1H-imidazol-4-yl)benzene (L) and 1,3,5-tri(4-carboxyphenyl)benzene (H₃BTB), respectively, have been achieved. Compound 1 is a porous three-dimensional (3D) framework with butterfly-like tetranuclear clusters as 7-connected nodes, and compund 2 is a 3D net with a different topology. Remarkably, compounds 1 and 2 exhibit selective adsorption of CO₂ over N₂ and methyl orange (MO) dye molecules. Magnetic measurements reveal that there are antiferromagnetic interactions within the tetranuclear cluster in 1. Furthermore, 2 was well-dispersed in different solvents, and their luminescent properties were investigated, and the results indicated that 2 could be considered as a potential luminescent probe for the detection of ketone molecules.

A hydrolytically stable uranyl organic framework for highly sensitive and selective detection of Fe3+ in aqueous media

A depleted uranium-based metal organic framework is synthesized and it exhibits highly sensitive and selective detection towards Fe³⁺ ions in aqueous media with an extremely low detection limit of 6.3 ppb.

A multifunctional microporous metal–organic framework: efficient adsorption of iodine and column-chromatographic dye separation

In this work, a multifunctional microporous metal–organic framework (MOF), [Cd(ABTC)(H₂O)₂(DMA)]·4DMA (JLNU-4; JLNU = Jilin Normal University; H₄ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid), has been synthesized based on the ligand H₄ABTC under solvothermal conditions. JLNU-4 shows excellent uptake of iodine both in solution and in the vapor phase, owing to the existence of a microporous structure in JLNU-4. The adsorption kinetics during the process of iodine adsorption were analyzed via a series of qualitative and quantitative analyses, such as the Langmuir and Freündlich adsorption isotherms. In addition, according to UV/vis spectroscopy analysis and the colour variance of JLNU-4, the relatively small sized dye methylene blue (MB) could be efficiently adsorbed by JLNU-4, through size-exclusion effects. Particularly, JLNU-4 can serve as a column-chromatographic filler for the separation of dye molecules. Therefore, JLNU-4 is a multifunctional microporous MOF for iodine adsorption and column-chromatographic dye separation.

JLNU-4 shows excellent uptake of iodine and could selectively adsorb dyes; therefore it can be used for column-chromatographic dye separation.

Anionic uranyl oxyfluorides as a bifunctional platform for highly selective ion-exchange and photocatalytic degradation of organic dyes

Anionic uranium oxyfluorides with tunable open-volumes were synthesized and they exhibit selective ion-exchange and photocatalytic properties toward methylene blue.

Structural Consequences of 1,4-Cyclohexanedicarboxylate Cis/Trans Isomerism in Uranyl Ion Complexes: From Molecular Species to 2D and 3D Entangled Nets

trans-1,4-Cyclohexanedicarboxylic acid (t-1,4-chdcH₂) or the commercially available mixture of the cis and trans isomers (c,t-1,4-chdcH₂) has been used in the synthesis of a series of 14 uranyl ion complexes, all obtained under solvohydrothermal conditions, some in the presence of additional metal cations and/or 2,2'-bipyridine (bipy). With its two isomeric forms having very different shapes and its great sensitivity to the experimental conditions, 1,4-chdc^2- appears to be suitable for the synthesis of uranyl ion complexes displaying a wide range of architectures. Under the conditions used, the pure trans isomer gives only the complexes [UO₂(t-1,4-chdc)(H₂O)₂] (1) and [UO₂(t-1,4-chdc)] (2), which crystallize as one- and two-dimensional (1D and 2D) species, respectively. Complexes containing either the cis isomer alone or mixtures of the two isomers in varying proportion were obtained from the isomer mixture. The neutral complexes [UO₂(c-1,4-chdc)(DMF)] (3) and [UO₂(c-1,4-chdc)(bipy)] (4) are 2D and 1D assemblies, respectively, while all the other complexes are anionic and include various counterions. [C(NH₂)₃]₃[H₂NMe₂][(UO₂)₄(c-1,4-chdc)₆]·H₂O (5) crystallizes as a three-dimensional (3D) framework with {10³} topology. While [H₂NMe₂]₂[(UO₂)₂(c-1,4-chdc)₂(t-1,4-chdc)]·DMF·2H₂O (6) is a 1D ladderlike polymer, [H₂NMe₂]₂[(UO₂)₂(c-1,4-chdc)(t-1,4-chdc)₂]·2H₂O (7), which differs in the cis/trans ratio, is a 3-fold 2D interpenetrated network with {6³} honeycomb topology. The related [H₂NMe₂]₂[(UO₂)₂(c,t-1,4-chdc)₃]·2.5H₂O (8), with one disordered ligand of uncertain geometry, is a 3-fold 3D interpenetrated system. The two isomorphous complexes [Co(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·1.5H₂O (9) and [Cd(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·1.5H₂O (10) form 3D frameworks with the {10³} srs topological type. In contrast, [Ni(bipy)₃]₂[(UO₂)₄(c-1,4-chdc)₂(t-1,4-chdc)(NO₃)₆]·2H₂O (11) is a molecular, tetranuclear complex due to the presence of terminal nitrate ligands. A 2-fold 3D interpenetration of frameworks with {10³} ths topology is observed in [Cu(bipy)₂]₂[(UO₂)₂(c-1,4-chdc)₂(t-1,4-chdc)]·2H₂O (12), while [Zn(bipy)₃][(UO₂)₂(c-1,4-chdc)₃]·4H₂O (13) crystallizes as a 2D net with the common {4.8²} fes topological type. The additional Pb^II cation is an essential part of the 3D framework formed in [UO₂Pb₂(c-1,4-chdc)(t-1,4-chdc)₂(bipy)₂] (14), in which uranyl and its ligands alone form 1D subunits. Together with previous results, the solid-state uranyl emission properties of seven of the present complexes evidence a general trend, with the maxima for the complexes with O₆ equatorial environments being blue-shifted with respect to those for complexes with O₅ environments.

Recent advances in structural studies of heterometallic uranyl-containing coordination polymers and polynuclear closed species

A survey is given of recent original structural results on heterometallic species incorporating uranyl ions, particularly with carboxylate ligands.

Four coordination polymers based on dinuclear and trinuclear units with a new multifunctional pyridyl-dicarboxylate ligand: luminescence and magnetic properties

Four coordination polymers with a new pyridyl-dicarboxylate ligand were synthesized under solvothermal conditions and studied by means of X-ray crystallography, topological analyses, luminescence and magnetic analyses.