Record High Iodate Anion Capture by a Redox-Active Cationic Polymer Network.

As a critical radioactive anionic contaminant, traditional adsorbents primarily remove iodate (IO3 -) through ion exchange or hard acid-hard base interactions, but suffer from limited affinity and capacity. Herein, employing the synergistic effect of ion exchange and redox, we successfully synthesized a redox-active cationic polymer network (SCU-CPN-6, [C9H10O2N5 ⋅ Cl]n) by merging guanidino groups with ion-exchange capability and phenolic groups with redox ability via a Schiff base reaction. SCU-CPN-6 exhibits a groundbreaking adsorption capacity of 896 mg/g for IO3 -. The inferior adsorption capacities of polymeric networks containing only redox (~0 mg/g) or ion exchange (232 mg/g) fragments underscore the synergistic "1+1>2" effect of the two mechanisms. Besides, SCU-CPN-6 shows excellent uptake selectivity for IO3 - in the presence of high concentrations of SO4 2-, Cl-, and NO3 -. Meanwhile, a high distribution coefficient indicates its exemplary deep-removal performance for low IO3 - concentration. The synergic strategy not only presents a breakthrough solution for the efficient removal of IO3 - but also establishes a promising avenue for the design of advanced adsorbents for diverse applications.

Near-Unity Energy Transfer from Uranyl to Europium in a Heterobimetallic Organic Framework with Record-Breaking Quantum Yield.

Lanthanide organic frameworks (Ln-MOFs) have attracted increasing research enthusiasm as photoluminescent materials. However, limited luminescence efficiency stemming from restricted energy transfer efficiency from the organic linker to the metal center hinders their applications. Herein, a uranyl sensitization approach was proposed to boost the luminescence efficiency of Ln-MOFs in a distinct heterobimetallic uranyl-europium organic framework. The record-breaking photoluminescence quantum yield (PLQY, 92.68%) among all reported Eu-MOFs was determined to benefit from nearly 100% energy transfer efficiency between UO22+ and Eu3+. Time-dependent density functional theory and ab initio wave-function theory calculations confirmed the overlap of excited state levels between UO22+ and Eu3+, which is responsible for the efficient energy transfer process. Coupled with intrinsically strong stopping power toward X-ray of the uranium center, SCU-UEu-2 features an ultralow detection limit of 1.243 µGyair/s, outperforming the commercial scintillator LYSO (13.257 µGyair/s) and satisfying the requirement of X-ray diagnosis (below 5.5 µGyair/s) in full.

Emergence of a Lanthanide Chalcogenide as an Ideal Scintillator for a Flexible X-ray Detector.

The development of high-performance X-ray detectors requires scintillators with fast decay time, high light yield, stability, and X-ray absorption capacity, which are difficult to achieve in a single material. Here, we present the first example of a lanthanide chalcogenide of LaCsSiS4 : 1 % Ce3+ that simultaneously integrates multiple desirable properties for an ideal scintillator. LaCsSiS4 : 1 % Ce3+ demonstrates a remarkably low detection limit of 43.13 nGyair s-1 and a high photoluminescence quantum yield of 98.24 %, resulting in a high light yield of 50480±1441 photons/MeV. Notably, LaCsSiS4 : 1 % Ce3+ exhibits a fast decay time of only 29.35±0.16 ns, making it one of the fastest scintillators among all lanthanide-based inorganic scintillators. Furthermore, this material shows robust radiation and moisture resistance, endowing it with suitability for chemical processing under solution conditions. To demonstrate the X-ray imaging capacity of LaCsSiS4 : 1 % Ce3+ , we fabricated a flexible X-ray detector that achieved a high spatial resolution of 8.2 lp mm-1 . This work highlights the potential of lanthanide chalcogenide as a promising candidate for high-performance scintillators.

Charge Transport and Photoconductivity in a Hybrid Uranium(IV) Halide Perovskite.

Hybrid metal halide perovskites are extensively synthesized using p- and d-elements. However, the properties of hybrid halide perovskites involving 5f-elements are still elusive. Herein, we first report the semiconductive property of a uranium-bearing hybrid halide perovskite, [N(C2H5)4]2UCl6 (EAUCl). Single crystal X-ray crystallography demonstrates that EAUCl adopts a zero-dimensional molecular structure consisting of isolated [UCl6]2- anions and organic cations. The intrinsically semiconductive property endows EAUCl with obvious charge transport and photoconductivity, with a high carrier mobility lifetime (µτ) product of 9.91 × 10-4 cm2/V and a photocurrent on-off ratio of 380 under X-ray excitation. Theoretical calculations corroborate that the U 5f orbitals are involved in electron transitions and the formation of band structure.

Turn-up Luminescent Sensing of Ultraviolet Radiation by Lanthanide Metal-Organic Frameworks.

Here, we report a series of two-dimensional lanthanide metal-organic frameworks Ln-DBTPA (where DBTPA = 2,5-dibromoterephthalic acid and Ln = Tb (1), Eu (2), or Gd (3)) showing a unique turn-up responsiveness toward ultraviolet (UV) radiation. The luminescence enhancement was derived from the accumulated radicals that can promote the intersystem crossing process. The compound 1 shows an ultralow detection limit of 9.1 × 10-9 J toward UV radiation, representing a new type of luminescent UV detectors.

Metal-Organic Framework@Metal Oxide Heterostructures Induced by Electron-Beam Radiation.

Metal organic frameworks (MOFs) are a distinct family of crystalline porous materials finding extensive applications. Their synthesis often requires elevated temperature and relatively long reaction time. We report here the first case of MOF synthesis activated by high-energy (1.5 MeV) electron beam radiation from a commercially available electron-accelerator. Using ZIF-8 as a representative for demonstration, this type of synthesis can be accomplished under ambient conditions within minutes, leading to energy consumption about two orders of magnitude lower than that of the solvothermal condition. Interestingly, by controlling the absorbed dose in the synthesis, the electron beam not only activates the formation reaction of ZIF-8, but also partially etches the material during the synthesis affording a hierarchical pore architecture and highly crystalline ZnO nanoparticles on the surface of ZIF-8. This gives rise to a new strategy to obtain MOF@metal oxide heterostructures, finding utilities in photocatalytic degradation of organic dyes.

Pioneering Iodine-125-Labeled Nanoscale Covalent Organic Frameworks for Brachytherapy.

Brachytherapy has been clinically used for the treatment of malignant solid tumors. However, the classic therapeutic radioactive 125I seed must be surgically implanted directly into tumors. To avoid the surgery and prevent irrational radioactive distribution, radioiodine-loaded nanomaterials are ever-developing for brachytherapy. Hence, it is still a notable challenge to obtain an advanced material that simultaneously incorporates features of high radiolabeling rate, short labeling time, good radiolabeling stability, and long tumor retention time. Covalent organic frameworks (COFs), which are crystalline polymers with ordered pores, are widely applied in guest delivery of drugs based on their high porosity and modifiable skeleton. Herein, we developed a functionalized nanoscale PEG-COF-Ag material, which could rapidly capture radioiodine reaching a 94% radiolabeling yield in 30 s. In addition, more than 95% 125I was maintained after 24 h in PBS (phosphate-buffered saline) as well as in serum and over 90% for nearly 1 week. PEG-COF-Ag-125I (125I-COF) demonstrated excellent cancer cell killing performance in vitro, and further experiments in vivo revealed a long tumor retention time and effective tumor treatment during the radiotherapy. The results indicate that radioiodine-labeled PEG-COF-Ag could be potentially applied in brachytherapy with a promising therapeutic effect.

Deuterated Covalent Organic Frameworks with Significantly Enhanced Luminescence.

Luminescent covalent organic frameworks (COFs) find promising applications in chemical sensing, photocatalysis, and optoelectronic devices, however, the majority of COFs are non or weakly emissive owing to the aggregation-caused quenching (ACQ) or the molecular thermal motion-based energy dissipation. Here, we report a previously unperceived approach to improve luminescence performance of COFs by introducing isotope effect, which is achieved through substitution of hydrogen from high-frequency oscillators X-H (X=O, N, C) by heavier isotope deuterium. Combining the "bottom-up" and in situ deuteration methods generates the first deuterated COF, which exhibits an impressively 19-fold enhancement in quantum yield over that of the non-deuterated counterpart. These results are interpreted by theoretical calculations as the consequence of slower C/N-D and OD⋅⋅⋅O vibrations that impede the nonradiative deactivation process. The proposed strategy is proved applicable to many other types of emissive COFs.

Thermoplastic Membranes Incorporating Semiconductive Metal-Organic Frameworks: An Advance on Flexible X-ray Detectors.

Semiconductive metal-organic frameworks (MOFs) have emerged in applications such as chemical sensors, electrocatalysts, energy storage materials, and electronic devices. However, examples of semiconductive MOFs within flexible electronics have not been reported. We present flexible X-ray detectors prepared by thermoplastic dispersal of a semiconductive MOF (SCU-13) through a commercially available polymer, poly(vinylidene fluoride). The flexible detectors exhibit efficient X-ray-to-electric current conversion with enhanced charge-carrier mobility and low trap density compared to pelleted devices. A high X-ray detection sensitivity of 65.86 µCGyair -1 cm-2 was achieved, which outperforms other pelleted devices and commercial flexible X-ray detectors. We demonstrate that the MOF-based flexible detectors can be operated at multiple bending angles without a deterioration in detection performance. As a proof-of-concept, an X-ray phase contrast under bending conditions was constructed using a 5×5 pixelated MOF-based imager.

Direct Radiation Detection by a Semiconductive Metal-Organic Framework.

Semiconductive metal-organic frameworks (MOFs) have attracted extraordinary research interest in recent years; however, electronic applications based on these emerging materials are still in their infancy. Herein, we show that a lanthanide-based semiconductive MOF (SCU-12) can effectively convert X-ray photons to electrical current signals under continuous hard X-ray radiation. The semiconductive MOF-based polycrystalline detection device presents a promising X-ray sensitivity with the value of 23.8 µC Gyair-1 cm-2 under 80 kVp X-ray exposure, competitive with the commercially available amorphous selenium (α-Se) detector. The lowest detectable X-ray dose rate is 0.705 µGy s-1, representing the record value among all X-ray detectors fabricated by polycrystalline materials. This work discloses the first demonstration of hard radiation detection by semiconductive MOFs, providing a horizon that can guide the synthesis of a new generation of radiation detection materials by taking the advantages of structural designability and property tunability in the MOF system.

Inorganic X-ray Scintillators Based on a Previously Unnoticed but Intrinsically Advantageous Metal Center.

Traditional inorganic X-ray scintillators are designed based on several representative metal ions (e.g., Tl+, Pb2+, Bi3+) with highly emissive nature and high atomic number aiming at the outstanding radiation stopping power. The combination of these two features gives rise to a high energy conversion efficiency from X-ray to visible emission, which is a prerequisite for an ideal scintillator and is currently one of the major limits for the further development of this field. Inspired by our recent observation on the intrinsic scintillating phenomenon in the heaviest naturally occurring element uranium, we report here a family of inorganic scintillators through combination of uranyl ions with diverse oxoanion groups (i.e., borate, phosphate, molybdate, germanate, etc.). Na2UO2(MoO4)2·(H2O) (UMO) is selected as a prototype of a uranyl-bearing inorganic scintillator, to show its intrinsic advantages in the X-ray excited luminescence (XEL), strong X-ray attenuation coefficient (XAC), reduced afterglow, and decent radiation stability, as compared with one of the most important commercial inorganic scintillators CsI:Tl.

Three Mechanisms in One Material: Uranium Capture by a Polyoxometalate-Organic Framework through Combined Complexation, Chemical Reduction, and Photocatalytic Reduction.

The design and synthesis of uranium sorbent materials with high uptake efficiency, capacity and selectivity, as well as excellent hydrolytic stability and radiation resistance remains a challenge. Herein, a polyoxometalate (POM)-organic framework material (SCU-19) with a rare inclined polycatenation structure was designed, synthesized through a solvothermal method, and tested for uranium separation. Under dark conditions, SCU-19 can efficiently capture uranium through ligand complexation using its exposed oxo atoms and partial chemical reduction from UVI to UIV by the low-valent Mo atoms in the POM. An additional UVI photocatalytic reduction mechanism can occur under visible light irradiation, leading to a higher uranium removal without saturation and faster sorption kinetics. SCU-19 is the only uranium sorbent material with three distinct sorption mechanisms, as further demonstrated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis.

A semiconducting uranium-organic framework based on a tetrathiafulvalene derivative.

A rare case of semiconducting actinide-based metal-organic framework SCU-125 was designed and synthesized. As a result of the lack of two coordination sites in the plane of the tetrathiafulvalene tetrabenzoate (TTFTB) molecule, a defective kgd network was formed. The electrical conductivity of SCU-125 was measured to be 2.2(2) × 10-7 S cm-1 at 25 °C ± 2 °C.

Efficient Sr-90 removal from highly alkaline solution by an ultrastable crystalline zirconium phosphonate.

We report here a distinct case of strontium removal under 1 M NaOH solution by an ultrastable crystalline zirconium phosphonate framework (SZ-7) with high adsorption capacity (183 mg g-1) and in-depth removal performance (Kd = 3.9 × 105 mL g-1), demonstrating the potential application of SZ-7 for 90Sr removal in highly alkaline nuclear waste.

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

Three (3,4)-connected uranyl-organic frameworks (UOFs) with pto and tbo topologies were synthesized. The UOF with a pto net possesses a 2-fold interpenetrating network and exhibits 2D interconnected channels. The UOF with a tbo net is constructed from two types of ultralarge nanocages. All these compounds can efficiently remove large cationic dye crystal violet (CV) through a cation exchange mechanism.

The fate of rhenium in polyaminocarboxy solution: Hourglass crystal and its speciation study.

This paper studied the fate of Re in the presence of polyaminocarboxy ligand (DTPA, EDTA and NTA) under reducing condition. When SnCl2 as reducing agent, the results indicated the low valent Re was formed. And batch experiments studied the effect of pH and different ligands on the formation of low valent Re complex, the acid condition was favoured for the formation of low valent Re complex, and the order of complexing toward the low valent Re was the following: DTPA > EDTA > NTA. In the condition of pH = 1, DTPA as ligand, the hourglass crystal was obtained. Using ESI-MS, solid-state UV-Vis-NIR spectra, EXAFS, DFT calculation et al, the darkened patch of the hourglass crystal was demonstrated to be Re, and its speciation was dimeric Re2(µ-O)2DTPA.

Benzotriazole decorated graphene oxide for efficient removal of U(VI).

There is a need to develop highly efficient materials for capturing uranium from nuclear wastewater. Here, 5-methylbenzotriazole modified graphene oxide (MBTA-GO) was used to adsorb U(VI) from aqueous solution. By the trials of different conditions, we found that the removal of U(VI) from acidic solution was strongly dependent on pH but independent of ionic strength. The U(VI) adsorption was perfectly conformed to the pseudo-second-order kinetics and the adsorption isotherms were simulated by the Langmuir model well. A high removal capacity (qmax = 264 mg/g) for U(VI) at pH 3.5 was obtained. XPS, EXAFS analyses and DFT calculations revealed that the mechanism of uranium capture was ascribed to (i) the surface complexation by benzotriazole and carboxyl groups (providing lone pair electrons) on MBTA-GO and (ii) enhanced synergistic coordination ability of delocalized π-bond of triazole group toward U due to the transfer of electrons from graphene sheet to benzotriazole. DFT calculations further demonstrated that benzotriazole displayed stronger binding with U(VI) compared to carboxyl group due to higher binding energy of [Side/Surface-U-MBTA-GO] (79.745, 54.986 kcal/mol) than [MBTA-GO-COOH-U] (27.131 kcal/mol). This work will provide valuable insight into designing novel nitrogen-containing adsorbents for practical application in wastewater treatment.

Interactions between uranium(vi) and phosphopeptide: experimental and theoretical investigations.

Uranium is an essential actinide element in nuclear fuel cycles, and protein phosphorylation is one type of most important post-translational modifications. It is of great interest to study the interactions between uranyl ions and phosphorylated proteins. In this study, a phosphorylated pentapeptide (WpTPpTW, P(1)) motif was designed as a model to mimic possible coordination sites in genuine phosphorylated proteins. Electrospray ionization mass spectrometry (ESI-MS) results suggested that uranyl-P(1) complexes with chemical stoichiometry of 1 : 1 and 1 : 2 were both available. The conditional stability constant of the 1 : 1 complex uranyl-P(1) was determined to be 6.6 ± 0.2 at pH 4.0 by tryptophan fluorescence titrations, which is almost three orders of magnitude higher than that of the complex of nonphosphorylated peptide. The results of extended X-ray absorption fine structure (EXAFS) combined with density functional theoretical calculations suggested that uranyl ions coordinated with one phosphoryl and carboxyl groups of P(1) in a mono-dentate fashion, and three water molecules. This study on the simple metal-peptide system could provide basic information for locating the uranyl coordination site in some important phosphorylated proteins which is useful for evaluating the chemical toxicity of uranyl in vivo.