Uranyl Organic Framework Research Articles

Photocatalytic Hydrogen Peroxide Production by a Mixed Ligand-Functionalized Uranyl-Organic Framework.

Hydrogen peroxide (H2O2) production driven by solar energy has received enormous attention due to its high efficiency, low cost, and environmental friendliness characteristics. Searching for new photocatalytic materials for H2O2 production is one of the most important targets. In this work, a new three-dimensional (3D) uranyl-organic framework material was constructed with mixed ligands via a solvothermal reaction and used for photocatalytic H2O2 production. The mixed ligand strategy not only benefits the construction of a 3D uranyl-organic framework but also introduces strong photon absorption groups into the framework. The thiophene and pyridine rings in the framework enhance photon absorption and carrier transfer. In addition, with the assistance of the hydrogen abstraction reaction of uranyl centers, the H2O2 production rate reaches 345 μmol h-1 g-1. This study provides a new blueprint for exploring the artificial photosynthesis of H2O2 through uranium-based metal-organic frameworks.

Preparation of a Nanosheeted Uranyl-Organic Framework for Enhanced Photocatalytic Oxidation of Toluene.

Preparation of ultrathin metal-organic framework (MOF) nanosheets is an effective way to improve the catalytic efficiency of MOF photocatalysts owing to their superiority in reducing the recombination rate of photogenerated electrons and holes and enhancing charge transfer. Herein, a light-sensitive two-dimensional uranyl-organic framework named HNU-68 was synthesized. Due to its interlayer stacking structure, the corresponding ultrathin nanosheets with a thickness of 4.4 nm (HNU-68-N) can be obtained through ultrasonic exfoliation. HNU-68-N exhibited an enhanced ability to selectively oxidize toluene to benzaldehyde, with the value of turnover frequency being approximately three times higher than that of the bulk HNU-68. This enhancement is attributed to the smaller size and interface resistance of the layered HNU-68-N nanosheets, which facilitate more thorough substrate contact and faster charge transfer, leading to an improvement in the photocatalytic efficiency. This work provides a potential candidate for the application of ultrathin uranyl-based nanosheets.

Enhanced hydrolytic stability and photocatalytic performance of a uranium‐based organic framework by hybrid carbon nanotubes

Owing to their highly predictable porous structures, facile synthesis, and the presence of functional open metal sites, metal–organic frameworks (MOFs) are extensively employed in various fields, including energy storage, catalysis, adsorption, and separation. Nevertheless, the limited hydrolytic stability exhibited by numerous MOFs poses a significant challenge to their practical application. In the present study, we present the synthesis and characterization of a uranyl organic framework (TCPP‐U1) with a highly porous structure, which is constructed by assembling cobalt, uranyl, and the porphyrin ligand 5,10,15,20‐tetra(4‐carboxyphenyl)porphyrin (TCPP). However, TCPP‐U1 demonstrates poor hydrolytic stability when exposed to water (the structure can be destroyed even after 2 min of exposure to water), greatly impeding its potential applications that would benefit from its high surface area. To address this limitation, we developed a hybrid composite by incorporating acid‐treated multi‐walled carbon nanotubes (CNTs) into the TCPP‐U1 framework via a solvothermal method designated as CNTs@TCPP‐U1. Remarkably, the obtained CNTs@TCPP‐U1 composite possesses an identical crystal structure and morphology to the original TCPP‐U1 yet exhibits significant enhancements in hydrolytic stability (the structure remains stable even after 3 days of immersion in water). Furthermore, CNTs@TCPP‐U1 demonstrates a significant photocatalytic effect on the degradation of tetracycline hydrochloride in aqueous solutions. The reaction rate constant (k) for the pseudo‐first‐order kinetic model is 0.0059 min−1. Our findings present a novel perspective for enhancing the stability and expanding the performance of MOFs materials.

Iodine capture of a two-dimensional layered uranyl-organic framework: a combined DFT and AIMD study.

To develop nuclear energy sustainably, it is important to effectively capture radioiodine in nuclear waste. In this study, we used density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations to investigate how well the uranyl-organic framework (UOF) could capture radioiodine. We found that the uranyl center and C-N ring sites in both cluster and periodic UOF models are very attractive to the I2 molecule. The adsorption energies of the I2 molecule in the periodic UOF models are as high as -1.10 eV, which is much higher than in the cluster model. The interaction characteristics between the I2 molecule and the UOF were revealed by electronic density topological analyses. Our AIMD simulations at 300 and 600 K have confirmed that the UOF has high adsorption kinetics for I2 molecules and can effectively capture them. The UOF has a high adsorption capacity and good adsorption stability for the I2 molecule, making it a promising option for the environmentally friendly removal of radioiodine.

Efficient adsorption and photocatalysis over a photorenewable uranyl-organic framework for removal of diquat herbicide

Adsorption and photocatalysis are generally considered an environmental friendliness and effective methods for eliminating organic pollutants. Developing bifunctional materials that integrate adsorption and photocatalysis can fully leverage the adsorption effect to increase the interaction between herbicides and photocatalysts, thus improving their photocatalytic degradation efficiency. To achieve the absorption and photocatalytic activity on contaminants, a light-sensitive three-dimensional uranyl-organic framework (UOF) named HNU-80 with an anionic skeleton was synthesized in this work. The charge characteristics of its electrostatic attraction with cations and the suitable band structure for producing reactive oxygen endow it with the potential for efficient adsorption and photocatalytic oxidation of the cationic diquat herbicide. The maximum adsorption capacity is up to 97.92 mg·g−1, and the adsorbed diquat could be completely degraded under light irradiation. In addition, the regenerated HNU-80 exhibits high reusability in subsequent adsorption cycle experiments. The adsorption mechanism is attributed to the electrostatic and π…π interaction between HNU-80 and diquat, while the photodegradation mechanism is due to the oxidation and decomposition of diquat by reactive oxygen species generated from the radiation of HNU-80. This work provides a promising candidate for the harmless treatment of organic pollutants, and the combination of photocatalytic property also promotes the regeneration of the UOF adsorbents for continued use.

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.

Synthesis, structure, and photocatalytic properties of a two-dimensional uranyl organic framework

Abstract A two-dimensional uranyl organic framework (UOF) UO2(L)(DMA) (1) (H2L = 2-aminoisophthalic acid, DMA = N, N-dimethylacetamide) has been solvothermally synthesized and characterized thoroughly by elemental analysis, infrared spectroscopy, single-crystal X-ray diffraction, solid fluorescence, powder X-ray diffraction, thermogravimetric analysis, and UV–visible spectroscopy. Furthermore, the degradation efficiencies of UOF 1 to organic dye methylene blue (MB) and rhodamine B (RhB) are 93.2 and 86.5% under irradiation of visible light which indicates that UOF 1 has remarkable photocatalytic activity. UOF 1 also displayed a certain selectivity for mixed dyes of MB & RhB.

Thiophene-functionalized heteronuclear uranium organic framework for selective detection and adsorption towards Mercury (II)

Mercury (II) metal ion is a headache problem due to its highly toxic and widely spread as an environmental pollutant. Herein, we design and synthesized a thiophene based heteronuclear uranyl organic framework {[Na(UO2)3(μ3-O)(μ2-OH)3(2,5-TDC)]•2H2O} (2,5-TDC ​= ​thiophene-2,5-dicarboxylic acid) (UOF1) for the selective sensing and adsorption towards Hg (II) in water. Among which, the regular 1D open channels and the accessible active soft base sulfur atoms arrayed on the pore walls play an important role for the Hg (II) grabbing and deposition, while the unique charge-transfer based “multi-peaks” fluorescent emission from the uranium centers act as the sensor towards the Hg (II). The detection limit and adsorption capacity are 2.488✕10−9 ​M and 244.32 ​mg ​g−1, respectively, which are among the top level performance for Hg (II) detection and remediation. In addition, density functional theory (DFT) calculations reveal that the Hg (II) affinity arising from the synergetic interactions of sulfur and oxygen supported by the UOF skeleton. This research demonstrates the dual functional utilization of a fluorescent MOF for both sensing and removal of metal ion, which highlights the facile construction of functionalized MOFs for heavy metals remediation.

Efficient Photocatalytic Oxidative Coupling of Benzylamine over Uranyl-Organic Frameworks.

Visible-light-driven organic transformation photocatalyzed by metal-organic frameworks (MOFs) under mild conditions is considered a feasible route to conserve energy and simplify synthesis. Herein, a light-sensitized, three-dimensional uranyl-organic framework (HNU-64) with twofold interpenetration and its derivatives HNU-64-CH3 and HNU-64-Cl with functionalized ligands of -CH3 and -Cl groups were obtained. These MOFs have broad optical absorption bands and suitable band energy levels in photooxidation, which makes them exhibit high activity and selectivity for the photooxidation of benzylamine to N-benzylbenzoimide under mild conditions. This work provides an efficient and simple synthetic option for oxidative coupling of amines to directly produce imines.

Synthesis, crystal structure, luminescent, and photocatalytic properties of a uranyl(VI)-organic framework based on tripodal flexible zwitterionic ligand

The uranyl-organic framework based tripodal flexible zwitterion ligand 1,1',1''-[benzene-1,3,5-triyltris(methylene)] tris(pyridine-4-carboxylic acid) tribromine (H3LBr3), [(UO2)2(μ3-O)(μ2-OH)L]NO3·nH2O (n ≈ 5) (1) has been synthesized under hydrothermal condition and characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and UV-visible spectroscopy. Compound 1 contains a tetra-uranyl oxo-cluster, which displays a microporous 3D structure. The fluorescence measurement shows that 1 exhibits strong luminescence. Furthermore, 1 shows good photocatalytic activity for the degradation of methylene blue.

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Double-Layer Nitrogen-Rich Two-Dimensional Anionic Uranyl-Organic Framework for Cation Dye Capture and Catalytic Fixation of Carbon Dioxide.

A novel two-dimensional double-layer anionic uranyl-organic framework, U-TBPCA {[NH2(CH3)2][(UO2)(TBPCA)], where H3TBPCA = 4,4',4″-s-triazine-1,3,5-triyltripamino-methylene-cyclohexane-carboxylate}, with abundant active sites and stability was obtained by assembling UO2(NO3)2·6H2O and a triazine tricarboxylate linker, TBPCA3-. Due to the flexibility of the ligand and diverse coordination modes between carboxyl groups and uranyl ions, U-TBPCA exhibits an intriguing topological structure and steric configuration. This double-layer anionic uranyl-organic framework is highly porous and can be used for selective adsorption of cationic dyes. Due to the presence of high-density metal ions and basic -NH- groups, U-TBPCA acts as an effective heterogeneous catalyst for the cycloaddition reaction of carbon dioxide with epoxy compounds. Moreover, the various modes of coordination between the tricarboxylic ligand and uranyl ion were studied by density functional theory calculations, and several simplified models were established to probe the influence of hydrogen bonding between carbon dioxide and U-TBPCA on the ability of U-TBPCA to bind carbon dioxide. This work should aid in improving our understanding of the coordination behavior of uranyl ion as well as the development and utilization of new actinide materials.

Creating and tailoring ultrathin two-dimensional uranyl-organic framework nanosheets for boosting photocatalytic oxidation reactions

The fabrication of ultrathin MOFs nanosheets (just single- or few-layer) is highly desired but seriously restricted by the relatively strong interactions between layers in layered MOFs precursors. Herein, for the first time, we employ a proof-of-concept weak supramolecular-interactions strategy to construct ultrathin uranyl-organic framework nanosheets. Impressively, the thickness of the resulting nanosheets is extremely thin down to only 1 nm, just equal to two layers, and also shows high dependence on the stacking mode of 2D uranyl MOFs precursors, for example, two layers in the eclipsed stacking mode vs. eight layers in the staggered stacking mode. Most importantly, this would significantly tailor their optical and electronic properties. As a result, the ultrathin nanosheet samples (two layers) present significantly enhanced photocatalytic oxidation activity compared to their pristine counterpart (4.5 times) and another nanosheet sample (eight layers, 2.2-fold). This work may open up a gate toward ultrathin uranyl-organic nanosheet for advanced functions.

U=O activation in uranyl-organic framework through solid-liquid reaction: A powerful tool to modulate electronic and magnetic structure

Activation of the extremely inert UO bond of uranyl group is presents not only a high scientific challenge, but also a powerful tool to modify the physical and chemical properties of materials with unique electronic and magnetic features. Distinct from all homogeneous methods of UO activation reported in the literature, this work presents, for the first time, a solid-liquid reaction through post-modification approach on uranyl-organic framework to generate stable U–O activated metal-organic framework. Two different molecules such as B-chlorocatecholborane (Cl-BCat) and diborane pinacolate ((Bpin)2, pin ​= ​pinacolate) were used to carry out this task, giving activating efficiency of 37% for Cl-BCat and 50% for (Bpin)2, respectively. Impressively, this UO activation directly leads to significant change in the physical and chemical properties, for example, a diamagnetic-to-paramagnetic transformation and significant reduction in photocatalytic oxidation efficiency, as compared to the properties of pristine MOF.

(UO2)(C10H8N2O2)2][HPW12O40]: The First Case of a Uranyl Coordination Network Containing a Keggin‐Type Polyoxometalate

A uranyl compound [(UO2)(C10H8N2O2)2][HPW12O40] has been hydrothermally synthesized (150 °C for 72 h) in the presence of typical Keggin‐phosphotungstic acid. This compound exhibits a regular layered structure which is composed of [UO2]2+ and bridging ligand 4,4'‐bipyridine‐N‐dioxide (4,4'‐BPDO). The nanosized cavities are occupied by Keggin‐anions [HPW12O40]2– through covalent bonds and hydrogen bonds, in order to hold the charge equilibrium and enhance the stability of the structure. The adsorption properties of this compound have been primarily investigated. The results indicate that the incorporation of Keggin‐anions plays an important role in the fast capture of cationic dye MB+. Compound 1 is the first case of uranyl coordination network decorated by POMs, which evidently provides a feasible strategy for controlling the structural connectivity and functionality of uranyl organic framework.

Stabilization of Photocatalytically Active Uranyl Species in a Uranyl–Organic Framework for Heterogeneous Alkane Fluorination Driven by Visible Light

When photoactivated, the uranyl ion is a powerful oxidant capable of abstracting hydrogen atoms from nonactivated C-H bonds. However, the highly reactive singly reduced [UVO2]+ intermediate is unstable with respect to disproportionation to the uranyl dication and insoluble tetravalent uranium phases, which limits the usage of uranyl ions as robust photocatalysts. Herein, we demonstrate that photoactivated uranyl ions can be stabilized by immobilizing and separating them spatially in a uranyl-organic framework heterogeneous catalyst, NU-1301. The visible-light-photoactivated uranyl ions in NU-1301 exhibited longer-lived U(V) and radicals than those in homogeneous counterparts, as evidenced by X-ray photoelectron spectroscopy and time-dependent electron paramagnetic resonance, leading to higher turnovers and enhanced stability for the fluorination of nonactivated alkanes.

Uranyl Organic Framework as a Highly Selective and Sensitive Turn-on and Turn-off Luminescent Sensor for Dual Functional Detection Arginine and MnO4.

Five new uranyl coordination polymers were prepared by the hydrothermal method based on 5-nitroisophthalic acid (H2nip) as (UO2)(nip)(2,2'-bpy) (1), (H24,4'-bpy)·[(UO2)3(nip)4]·(4,4'-bpy) (2), (H2bpe)·[(UO2)0.5(nip)] (3), (H2 bpp)·[(UO2)2-(nip)3]·H2O (4), and (H2tmp)·[(UO2)(nip)2](5) [2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine, bpe = 4,4'-vinylenedipyridine, bpp = 4,4' -trimethylenedipyridine, tmp = tetramethylpyrazine]. All of these synthesized complexes have been characterized by single crystal and powder X-ray diffraction, IR spectra, thermogravimetric analysis, elemental analysis, and luminescent properties. In particular, it is found that compounds 1 and 4 can be used as a luminescent sensor to efficiently detect arginine in aqueous solution by means of "turn-on"; the detection limits were 1.06 × 10-6 and 6.42 × 10-6 mol/L, respectively. Moreover, 4 can also be used as a bifunctional sensor for selective sensing of MnO4- anion by "turn-off". The detection limit of MnO4- in water was 1.79 × 10-6 mol/L; the Ksv was 1.88 × 104. The sensing effect of arginine in simulated grape juice samples and MnO4- in simulated river water samples was also investigated by this sensing system with high recovery. In addition, the possible mechanism of sensing arginine and MnO4- in the aqueous solution was discussed.

Triazine Functionalized Porous Three-Dimensional Uranyl–Organic Framework: Extraction of Uranium(VI) and Adsorption of Cationic Dyes in Aqueous Solution

A novel uranyl-organic framework [(CH3)2NH2]2.5·(UO2)2.5(TDPAT)(TDPAT*)0.5·6.5H2O with abundant active sites and water stability was obtained by assembling high-valence U(VI) cation and triazine hexacarboxylate ligand H6TDPAT {H6TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine; TDPAT* = [2,4-di(3,5-dicarboxylphenylamino)-6-(3-carboxylphenylamino)[-1,3,5-triazine}. As far as we know, this is the first uranium-based metal–organic framework constructed by inorganic building bricks [UO2(RCOO)2O]–, [UO2(RCOO)3]–, and [UO2(RCOO)2OO] and triazine hexacarboxylate ligand, which exhibits an interesting structural arrangement with three-dimensional topology. In order to broaden its functional characteristics, we first investigated the functional adsorbent for extraction of uranium(VI) and adsorption of cationic dyes in aqueous solution. It exhibits excellent performance in extracting uranium from aqueous solution and is not affected by other interfering metal ions. This work shows for the first time the ...

A Water-Stable Uranyl Organic Framework as a Highly Selective and Sensitive Bifunctional Luminescent Probe for Fe3+ and Tetracycline Hydrochloride.

A new coordination polymer (H2 bpy)0.5 ⋅[(UO2 )1.5 (ipa)2 (H2 O)] (1) (H2 ipa=isophthalic acid, bpy=4,4'-bipyridine) was synthesized by hydrothermal condition. It was characterized by IR spectroscopy, elemental analysis, TG-DTA analysis, and powder X-ray diffraction. Analysis of single-crystal X-ray diffraction results showed that the title compound exhibited a double chain bridged by the different uranyl ions and ipa2- ligands. Through the hydrogen bond interactions and π⋅⋅⋅π stacking interactions, the double chains were assembled into the three-dimensional supramolecular framework. Furthermore, the compound can be used as a promising bifunctional luminescence sensor for detecting and identifying Fe3+ and tetracycline hydrochloride antibiotic molecules with high selectivity and sensitivity in aqueous solutions. Moreover, the luminescent sensing mechanisms for different analytes were proposed. Moreover, the electronic properties of title compound were explored by density functional theory (DFT) calculations. The sensor system has been successfully applied for the detection of Fe3+ and tetracycline hydrochloride with high recovery percentages and low relative standard deviation in real river water samples.

Metal-Carboxyl Helical Chain Secondary Units Supported Ion-Exchangeable Anionic Uranyl-Organic Framework.

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 )2 NH2 ]+ ions in its open channels, as evidenced by a combination of 1 H NMR spectroscopy, EDS and PXRD.