A MOF@Metal Oxide Heterostructure Induced by Post-Synthetic Gamma-Ray Irradiation for Catalytic Reduction.

Metal-organic framework (MOF) based heterostructures, which exhibit enhanced or unexpected functionality and properties due to synergistic effects, are typically synthesized using post-synthetic strategies. However, several reported post-synthetic strategies remain unsatisfactory, considering issues such as damage to the crystallinity of MOFs, presence of impure phases, and high time and energy consumption. In this work, we demonstrate for the first time a novel route for constructing MOF based heterostructures using radiation-induced post-synthesis, highlighting the merits of convenience, ambient conditions, large-scale production, and notable time and energy saving. Specifically, a new HKUST-1@Cu2O heterostructure was successfully synthesized by simply irradiating a methanol solution dispersed of HKUST-1 with gamma ray under ambient conditions. The copper source of Cu2O was directly derived from in situ radiation etching and reduction of the parent HKUST-1, without the use of any additional copper reagents. Significantly, the resulting HKUST-1@Cu2O heterostructure exhibits remarkable catalytic performance, with a catalytic rate constant nearly two orders of magnitude higher than that of the parent HKUST-1.

Photochromic Uranyl-Based Coordination Polymer for Quantitative and On-Site Detection of UV Radiation Dose.

A highly sensitive detection of ultraviolet (UV) radiation is required in a broad range of scientific research, chemical industries, and health-related applications. Traditional UV photodetectors fabricated by direct wide-band-gap inorganic semiconductors often suffer from several disadvantages such as complicated manufacturing procedures, requiring multiple operations and high-cost instruments to obtain a readout. Searching for new materials or simple strategies to develop UV dosimeters for quantitative, accurate, and on-site detection of UV radiation dose is still highly desirable. Herein, a photochromic uranyl-based coordination polymer [(UO2)(PBPCA)·DMF]·DMF (PBPCA = pyridine-3,5-bis(phenyl-4-carboxylate), DMF = N,N'-dimethylformamide, denoted as SXU-1) with highly radiolytic and chemical stabilities was successfully synthesized via the solvothermal method at 100 °C. Surprisingly, the fresh samples of SXU-1 underwent an ultra-fast UV-induced (365 nm, 2 mW) color variation from yellow to orange in less than 1 s, and then the color changed further from orange to brick red after the subsequent irradiation, inspiring us to develop a colorimetric dosimeter based on red-green-blue (RGB) parameters. The mechanism of radical-induced photochromism was intensively investigated by UV-vis absorption spectra, EPR analysis, and SC-XRD data. Furthermore, SXU-1 was incorporated into an optoelectronic device to fabricate a novel dosimeter for convenient, quantitative, and on-site detection of UV radiation dose.

Self-Aggregated Nanoscale Metal-Organic Framework for Targeted Pulmonary Decorporation of Uranium.

The limited availability of effective agents for removing actinides from the lungs significantly restricts the effectiveness of medical treatments for nuclear emergencies. Inhalation is the primary route of internal contamination in 44.3% of actinide-related accidents, leading to the accumulation of radionuclides in the lungs and resulting in infections and potential tumor formation (tumorigenesis). This study focuses on the synthesis of a nanometal-organic framework (nMOF) material called ZIF-71-COOH, which is achieved by post-synthetic carboxyl functionalization of ZIF-71. The material demonstrates high and selective adsorption of uranyl, while also exhibiting increased particle size (≈2100 nm) when it aggregates in the blood, enabling passive targeting of the lungs through mechanical filtration. This unique property facilitates the rapid enrichment and selective recognition of uranyl, making nano ZIF-71-COOH highly effective in removing uranyl from the lungs. The findings of this study highlight the potential of self-aggregated nMOFs as a promising drug delivery system for targeted uranium decorporation in the lungs.

Boosting Simultaneous Uranium Decorporation and Reactive Oxygen Species Scavenging Efficiency by Lacunary Polyoxometalates.

The chemical toxicity and the oxidative stress induced by the internal exposure of uranium is responsible for the long-term adverse effect of in vivo contamination of uranium. An agent with simultaneous removal capability of uranium and excess reactive oxygen species (ROS) is highly desired. Herein, the lacunary Keggin-type polyoxometalate (POM) is demonstrated to selectively bind with uranyl ions in the presence of excess essential divalent ions and exhibits a compelling ROS scavenging efficiency of 78.8%. In vivo uranium decorporation assays illustrate the uranium sequestration efficiencies of 74.0%, 49.4%, and 37.1% from kidneys by prophylactic, prompt, and delayed administration of lacunary POM solution, respectively. The superior ROS quenching and uranium removal performance in comparison with all reported bifunctional agents endow lacunary polyoxometalates as novel agents to effectively protect people from injuries caused by the internal exposure of actinides.

Effective mitigation of gadolinium deposition using the bidentate hydroxypyridinone ligand Me-3,2-HOPO.

With the extensive usage of gadolinium-based contrast agents (GBCAs) in magnetic resonance imaging (MRI), gadolinium deposition has been observed in the brain, kidneys, liver, etc., and this is also closely related to the development of nephrogenic systemic fibrosis (NSF) in patients with renal dysfunction. Chelation, thereby promoting the elimination of deposited Gd(III), seems to be promising for alleviating these problems. Despite many ligands suitable for chelation therapy having been studied, the decorporation of transition metals (e.g. iron, copper, lead, etc.) and actinides (e.g. uranium, plutonium, etc.) has long been a primary concern, whereas the study of Gd(III) has been extremely limited. Due to their excellent metal binding abilities in vivo and therapeutic effects toward neurodegenerative diseases, bidentate hydroxypyridinone ligands are expected to be able to remove Gd(III) from the brain, kidneys, bones, and liver. Herein, the Gd(III) decorporation efficacy of a bidentate hydroxypyridinone ligand (Me-3,2-HOPO) has been evaluated. The complexation behavior between Me-3,2-HOPO and Gd(III) in solution and solid states was characterized with the assistance of potentiometric titration and X-ray diffraction techniques, respectively. Solution-based thermodynamic studies illustrate that the dominant species of complex between Gd(III) and Me-3,2-HOPO (HL) is GdL2+ (log ß120 = 11.8 (3)) at pH 7.4. The structure of the Gd-Me-3,2-HOPO crystal obtained from a room temperature reaction reveals the formation of a Gd(III) dimer that is chelated by four ligands as a result of metal ion hydration and ligand complexation. Cellular Gd(III) removal assays illustrate that Me-3,2-HOPO could effectively reduce final amounts of gadolinium by 77.6% and 66.1% from rat renal proximal tubular epithelial (NRK-52E) cells and alpha mouse liver 12 (AML-12) cells, respectively. Our current results suggest the potential of bidentate HOPO ligands as an effective approach to treat patients suffering from Gd(III) toxicity.

In Vivo Uranium Decorporation by a Tailor-Made Hexadentate Ligand.

The sequestration of uranium, particularly from the deposited bones, has been an incomplete task in chelation therapy for actinide decorporation. Part of the reason is that all previous decorporation ligands are not delicately designed to meet the coordination requirement of uranyl cations. Herein, guided by DFT calculation, we elaborately design a hexadentate ligand (TAM-2LI-MAM2), whose preorganized planar oxo-donor configuration perfectly matches the typical coordination geometry of the uranyl cation. This leads to an ultrahigh binding affinity to uranyl supported by an in vitro desorption experiment of uranyl phosphate. Administration of this ligand by prompt intraperitoneal injection demonstrates its uranyl removal efficiencies from the kidneys and bones are up to 95.4% and 81.2%, respectively, which notably exceeds all the tested chelating agents as well as the clinical drug ZnNa3-DTPA, setting a new record in uranyl decorporation efficacy.

Developing a Unique Hydrogen-Bond Network in a Uranyl Coordination Framework for Fuel Cell Applications.

Crystalline materials with persistent high anhydrous proton conductivity that can be directly used as a practical electrolyte of the intermediate-temperature proton exchange membrane fuel cells for durable power generation remain a substantial challenge. The present work proposes a unique way of the axial uranyl oxo atoms as hydrogen-bond acceptors to form a dense hydrogen-bonded network within a stable uranyl-based coordination polymer, UO2(H2PO3)2(C3N2H4)2 (HUP-3). It exhibits stable and efficient anhydrous proton conductivity over a super-wide temperature range (-40-170 °C). It was also assembled into a H2/O2 fuel cell as the electrolyte and shows a high electrical power density of 11.8 mW·cm-2 at 170 °C, which is among one of the highest values reported from crystalline solid electrolytes. The cell was tested for over 12 h without notable power loss.

Hinokitiol, an Advanced Bidentate Ligand for Uranyl Decorporation.

Despite the critical role actinide decorporation agents play in the emergency treatment of people in nuclear accidents and other scenarios that may cause internal contamination of actinides, new ligands have seldom been reported in recent decades because the current inventory has been limited to only a handful of functional groups. Therefore, new functional groups are always being urgently sought for the introduction of advanced actinide decorporation agents. Herein, a tropolone derivative, 2-hydroxy-6-(propan-2-yl)cyclohepta-2,4,6-trien-1-one (Hinokitiol or Hino), is proposed to be a promising candidate for this purpose by virtue of its well-demonstrated high membrane permeability and high affinity for metal ions. The coordination stoichiometry of Hino with uranyl is demonstrated to be 3:1 both in an aqueous solution (pH 7.4) and in the solid state. The results of a liquid-liquid extraction experiment further show that Hino exhibits strong chelating ability and selectivity toward uranyl over biological essential metal ions (i.e., Mn2+, Zn2+, Co2+, and Ni2+) with an extraction efficiency of >90.0%. The in vivo uranyl removal efficacies of Hino in kidneys and bone of mice are demonstrated to be 67.0% and 32.3%, respectively. On the basis of the observations described above, it is highly possible that further modification of Hino will lead to a large family of multidentate agents with enhanced uranyl decorporation ability.

Development and Characterization of a Novel Hydrogel for the Decontaminating of Radionuclide-Contaminated Skin Wounds.

Designing skin decontaminating materials with outstanding therapeutic effects, adhesiveness, and suitable mechanical property has great practical significance in radionuclide-contaminated skin wound healing. Here, a physically crosslinked hydrogel is constructed via hydrogen bonding of poly acrylamide, sodium alginate (SA), and the complexing agent diethylene triamine pentaacetic acid (DTPA). The physical and chemical properties of the poly(AAm-SA-DTPA) hydrogel (PASD) are detected according to established methods. The decontaminating property and skin wound healing of the PASD are investigated to confirm multi-functions of wound dressing. The physical and chemical properties results show that the synthesis of the PASD hydrogel is effective and that DTPA is present in the hydrogel. The hydrogel also shows great mechanical and swelling properties. In vitro tests find that PASD shows significant scavenging abilities for strontium and cerium. In vivo experiments show that the PASD hydrogel can remove radioactive strontium from the skin wounds of mice, and can effectively prevent the absorption of radioactive strontium through the skin wound. Furthermore, the PASD hydrogel can effectively promote the formation of granulation tissue in a radioactive contaminated wound. Taken together, the PASD hydrogels, which has good mechanical properties and radionuclides decontamination, is expected to be used as a dressing for radionuclide-contaminated skin wound healing.

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.

Intrinsic Semiconducting Behavior in a Large Mixed-Valent Uranium(V/VI) Cluster.

We disclose the intrinsic semiconducting properties of one of the largest mixed-valent uranium clusters, [H3 O+ ][UV (UVI O2 )8 (µ3 -O)6 (PhCOO)2 (Py(CH2 O)2 )4 (DMF)4 ] (Ph=phenyl, Py=pyridyl, DMF=N,N-dimethylformamide) (1). Single-crystal X-ray crystallography demonstrates that UV center is stabilized within a tetraoxo core surrounded by eight uranyl(VI) pentagonal bipyramidal centers. The oxidation states of uranium are substantiated by spectroscopic data and magnetic susceptibility measurement. Electronic spectroscopy and theory corroborate that UV species serve as electron donors and thus facilitate 1 being a n-type semiconductor. With the largest effective atomic number among all reported radiation-detection semiconductor materials, charge transport properties and photoconductivity were investigated under X-ray excitation for 1: a large on-off ratio of 500 and considerable charge mobility lifetime product of 2.3×10-4  cm2 V-1 , as well as a high detection sensitivity of 23.4 µC Gyair -1 cm-2 .

In Vivo Uranium Sequestration using a Nanoscale Metal-Organic Framework.

An agent for actinide sequestration with fast uranium uptake kinetics and efficient in vivo uranium removal using a nanoscale metal-organic framework (nano-MOF) is proposed. UiO-66 nanoparticles post-synthetically functionalized with carboxyl groups, UiO-66-(COOH)4 -180, exhibit the fastest uranium uptake kinetics reported with more than 65 % of uranyl in fetal bovine serum (FBS) removed within 5 min. Moreover, the in vivo bio-distribution studies show that the material partially accumulates in kidneys and femurs where uranium mainly deposits facilitating the in vivo sequestration of uranium. The results of the in vivo uranium decorporation assays with mice show that UiO-66-(COOH)4 -180 could successfully reduce the amounts of uranyl deposited in kidneys and femurs by up to 55.4 % and 36.5 %, respectively, and is significantly more efficient than the commercial actinide decorporation agent, ZnNa3 -DTPA.

Full-Range Ratiometric Detection of D2O in H2O by a Heterobimetallic Uranyl/Lanthanide Framework with 4f/5f Bimodal Emission.

A uranyl-europium heterobimetallic compound, (TEA)3[(UO2)6Eu(H2O)4(PPA)6] (H3PPA = phosphonoacetic acid, TEA = tetraethylammonium cation), was synthesized under mild hydrothermal conditions. The emission spectrum contains characteristic electronic transition features of both Eu3+ and UO22+, while the peak intensity of Eu3+ is notably higher than that of UO22+. This is primarily attributed to the energy transfer from uranyl to europium in the structure. Significantly, a positive correlation between the Eu3+ peak intensity at 621 nm and the D2O content can be established in the aqueous system, while the uranyl peak intensity is almost unchanged, allowing for the full-range ratiometric detection of D2O in H2O.

Amidoxime-Functionalized Covalent Organic Nanosheets for Sequestration of Uranium In Vivo.

Finding efficient actinide decorporation agents is crucial for public health and the development of the nuclear industry. The current inventory of decorporation agents is predominately limited to a handful of ligands. In this work, a two-dimensional (2D) covalent organic nanosheet (CON) material was rationally designed and tested for in vivo uranium decorporation. This material is extensively grafted with amidoxime (AO), a classic uranium-recognition ligand, which not only provides selective binding sites for uranyl but also expands the interlayer spacing of CON, making the active sites more accessible. Significantly, the results of in vivo experiments demonstrate that, in both prophylactic and prompt administration groups, CON-AO exhibits a higher excretion ratio of uranium from kidneys than that of ZnNa3-diethylenetriamine pentaacetate (DTPA), while presenting a similar level of cytotoxicity. These results suggest that functionalized CONs may emerge as a promising type of actinide in vivo decorporation agent.

A unique uranyl framework containing uranyl pentamers as secondary building units: synthesis, structure, and spectroscopic properties.

Two three-dimensional uranyl framework compounds consisting of 1,2,4-benzenetricarboxylic ligands and uranyl units have been synthesized under mild solvothermal conditions. Compound 1 adopts an open framework structure built from uranyl pentamers, which is a rare topology for uranyl structures. Compound 2 is constructed from UO8 and UO7 bipyramids that are connected by the ligand to form a three-dimensional framework. As a consequence, compound 1 exhibits an unusual photoluminescence spectrum of one broad peak at 545 nm with a significant red shift compared to the typical uranyl emissive peaks as shown in the spectra of uranyl nitrate and compound 2. In addition, since compound 1 crystallizes in the noncentrosymmetric space group Cc, its secondary-harmonic generation property was measured under 1064 nm laser radiation, showing a moderate SHG signal response of 0.91 × KDP.

A hydrolytically stable anionic layered indium-organic framework for the efficient removal of 90Sr from seawater.

Efficient removal of radioactive 90Sr from nuclear waste solutions and natural water systems is of vital importance due to its radioactive nature and high mobility. We present here an anionic layered compound (NC4H12)(NC2H8)2[In3(pydc)6]·13.1H2O (SZ-6; pydc = 2,5-pyridinedicarboxylic acid) with the potential remediation ability towards radioactive Sr2+ from seawater. This material exhibits excellent ß and γ radiation resistance both in air and in aqueous solutions. Besides, this material could maintain its structural integrity in real seawater for 77 days. The adsorption experiment results show that SZ-6 exhibits superior Sr2+ removal capability over a wide pH range from 4 to 12 with fast adsorption kinetics and high selectivity. The effective removal of 90Sr from real seawater was demonstrated as well. Our results strongly suggest the potential application of SZ-6 for selectively capturing radionuclides in natural water systems.

Photo-exfoliation of a highly photo-responsive two-dimensional metal-organic framework.

When exposed to UV (365 nm, 2 mW) radiation, the bulk crystals of a two-dimensional metal-organic framework [Hphen]2[(UO2)2(ox)3] (1,phen = 1,10-phenanthroline, ox = oxalate) are exfoliated into thin sheets (2 µm) and its photoluminescence can be quenched in an incredibly sensitive manner, setting 1 as a superior UV-detection material. When upgrading the UV source into a 300 W xenon light source, the crystals of 1 can be further exfoliated into monolayer nanosheets (0.92 nm).

Contribution of Human Hair in Solar UV Transmission in Skin: Implications for Melanoma Development.

Melanoma is the deadliest type of skin cancer with its prevalence on the rise. Recently, the melanocyte stem cells in hair follicles have been identified as the possible origin of melanoma upon exposure to ultraviolet radiation (UVR) through skin. It is hypothesized that colourless vellus hair (predominant in childhood) can serve as an alternative pathway in transmitting these ultraviolet (UV) photons to the stem cells. To investigate this, we have used the CRAIC microspectrophotometer to investigate the optical properties of 'vellus-like' hairs and terminal hairs of different colours using UV-VIS-NIR light sources. It was found that the average attenuation coefficient of 'vellus-like' hair is significantly lower than that of terminal hair in the UVA (p < 0.0001) and UVB (p < 0.001) wavelength ranges. Next, the optical properties of hairs are applied to simulations for examining their influence on UV transmission into the skin. The results show that the presence of vellus hair would increase the solar UV transmission to the melanocyte stem cell layer significantly. The findings explain why children are particularly vulnerable to sun exposure and the positive correlation found between the incidence of melanoma in adults' bodies and the number of vellus hairs in these areas.

A 3,2-Hydroxypyridinone-based Decorporation Agent that Removes Uranium from Bones In Vivo.

Searching for actinide decorporation agents with advantages of high decorporation efficiency, minimal biological toxicity, and high oral efficiency is crucial for nuclear safety and the sustainable development of nuclear energy. Removing actinides deposited in bones after intake is one of the most significant challenges remaining in this field because of the instantaneous formation of highly stable actinide phosphate complexes upon contact with hydroxyapatite. Here we report a hydroxypyridinone-based ligand (5LIO-1-Cm-3,2-HOPO) exhibiting stronger affinity for U(VI) compared with the reported tetradentate hydroxypyridinone ligands. This is further revealed by the first principles calculation analysis on bonding between the ligand and uranium. Both in vitro uranium removal assay and in vivo decorporation experiments with mice show that 5LIO-1-Cm-3,2-HOPO can remove uranium from kidneys and bones with high efficiencies, while the decorporation efficiency is nearly independent of the treatment time. Moreover, this ligand shows a high oral decorporation efficiency, making it attractive for practical applications.

3-Hydroxy-2-Pyrrolidinone as a Potential Bidentate Ligand for in Vivo Chelation of Uranyl with Low Cytotoxicity and Moderate Decorporation Efficacy: A Solution Thermodynamics, Structural Chemistry, and in Vivo Uranyl Removal Survey.

Uranium poses a threat for severe renal and bone damage in vivo. With the rapid development of nuclear industry, it is more urgent than ever to search for potential in vivo uranium chelators. In this work, 3-hydroxy-2-pyrrolidinone (HPD) is investigated as a new potential uranium decorporation ligand. The potentiometric titration measurements were carried out, and the stability constants were determined to be log ß110 = 10.5(7), log ß120 = 20.7(9), and log ß130 = 28.2(4). The species distribution diagram shows that nearly all uranyl is complexed by HPD at pH 7.4 under the defined condition. A single crystal of uranyl and HPD complexes, [(UO2)3O(H2O)3(C4H6NO2)3]·NO3·12H2O (uranyl-HPD), was obtained via an evaporation method. The overall structure of uranyl-HPD is a trimer that consists of three uranyl units and three HPD ligands. The uranyl unit is equatorially coordinated by three oxygen atoms from two HPD agents, one coordinated water molecule, and one µ3-O atom that is shared by three uranyl units. The results of the cytotoxicity assay indicate that the ligand is less toxic than the chelators used clinically (i.e., DTPA-ZnNa3 and 3-hydroxy-1,2-dimethyl-4(1 H)-pyridone (DFP)). The results of the uranium removal assay using the NRK-52E cell show that it could reduce as much as 58% of the uranium content at the cellular level. Furthermore, the in vivo uranium decorporation assays demonstrate that HPD can remove 52% of uranium deposited in the kidney but shows poor uranium removal efficacy in the bone.