Radiation-Assisted Assembly of a Highly Dispersed Nanomolybdenum-Functionalized Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D COFs), featuring a large surface area and 1D pore structure, serve as promising scaffolds for anchoring functional guest compounds, which can significantly enhance their performance and thus expand their potential applications. Postsynthetic strategy for COFs functionalization is versatile but challenging because of their tedious procedure with high time and energy consumption, generation of excess reaction waste, and damage to COF crystallinity. We report in this work a general strategy for the synthesis of inorganic nanocompound-functionalized COF composites in a one-pot way. Specifically, a high-crystallinity nanoscale molybdenum compound is successfully introduced into a COF skeleton with high dispersion in situ during the crystallization process of the COF induced by gamma ray radiation under ambient conditions. The obtained COF@Mo composites exhibit remarkable sorption performance for methylene blue and many other organic dyes in aqueous solution with the advantages of ultrarapid uptake dynamics and high removal efficiency.

Theoretical insights into selective extraction of Am(III) from Cm(III) and Eu(III) with asymmetric N-heterocyclic ligands.

Separation of lanthanide (Ln) and minor actinide (MA) elements and mutual separation between minor actinide elements (e.g. Am(III) and Cm(III)) represent a crucial undertaking. However, separating these elements poses a significant challenge owing to their highly similar physicochemical properties. Asymmetric N-heterocyclic ligands such as N-ethyl-6-(1H-pyrazol-3-yl)-N-(p-tolyl)picolinamide (Et-p-Tol-A-PzPy) and N-ethyl-N-(p-tolyl)-1,10-phenanthroline-2-carboxamide (ETPhenAm) have recently received considerable attention in the separation of MAs over Ln from acid solutions. By changing the central skeleton structures of these ligands and introducing substituents with different properties on the side chains, their complexation behavior with Am(III), Cm(III), and Eu(III) may be affected. In this work, we explore four different asymmetric N-containing heterocyclic ligands, namely Et-p-Tol-A-PzPy (L1), N-ethyl-6'-(1H-pyrazol-3-yl)-N-(p-tolyl)-[2,2'-bipyridine]-6-carboxamide (L2), N-ethyl-9-(1H-pyrazol-3-yl)-N-(p-tolyl)-1,10-phenanthroline-2-carboxamide (L3), and ETPhenAm (L4) using density functional theory (DFT). The calculated results demonstrate the potential of ligands L1-L4 for the extraction and separation of Am(III), Cm(III), and Eu(III). Ligand analysis shows that ligand L3 binds more easily to the central metal atom, in line with the stronger extraction capacity of L3. In spite of the higher covalence between the side chain and the central metal atom for complexes with L1-L3, the main chain seems to control the stability of the extraction complexes. The preorganized 1,10-phenanthroline backbone also further enhances the extraction performance of L3 and L4. The difference in coordination ability between the side chain donors of these ligands and metal ions may affect their separation efficiency. This work presents theoretical insights into synthesizing novel ligands for separating trivalent actinides by adjusting N-heterocyclic ligands.

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.

Dual-Phase Structure through Selective Etching of the Double A-Element MAX Phase in Lewis Acidic Molten Salts.

Two-dimensional (2D) MXene materials with innovative properties and versatile applications have gained immense popularity among scientists. The green and environmentally friendly Lewis acid salt etching route has opened up immense possibilities for the advancement of 2D MXene materials. In this study, we precisely etched the Al element from the double A-element MAX phases Ti2(SnyAl1-y)C by employing Lewis molten salt guided by redox potentials. This approach led to the discovery of a novel Ti2SnyCClx dual-phase structure consisting of Ti2SnC and Ti2CClx. We then established that the etching of the MAX phase via Lewis acid salt is facilitated by the oxidation of M-site elements, with the MX sublayer acting as an electron transmission conduit to enable the oxidation of A-site elements. This work is dedicated to unraveling the underlying mechanisms governing the etching processes using Lewis molten salt, thereby contributing to a more profound comprehension of these innovative etching routes.

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.

Creation of Cationic Polymeric Nanotrap Featuring High Anion Density and Exceptional Alkaline Stability for Highly Efficient Pertechnetate Removal from Nuclear Waste Streams.

There is an urgent need for highly efficient sorbents capable of selectively removing 99TcO4- from concentrated alkaline nuclear wastes, which has long been a significant challenge. In this study, we present the design and synthesis of a high-performance adsorbent, CPN-3 (CPN denotes cationic polymeric nanotrap), which achieves excellent 99TcO4- capture under strong alkaline conditions by incorporating branched alkyl chains on the N3 position of imidazolium units and optimizing the framework anion density within the pores of a cationic polymeric nanotrap. CPN-3 features exceptional stability in harsh alkaline and radioactive environments as well as exhibits fast kinetics, high adsorption capacity, and outstanding selectivity with full reusability and great potential for the cost-effective removal of 99TcO4-/ReO4- from contaminated water. Notably, CPN-3 marks a record-high adsorption capacity of 1052 mg/g for ReO4- after treatment with 1 M NaOH aqueous solutions for 24 h and demonstrates a rapid removal rate for 99TcO4- from simulated Hanford and Savannah River Site waste streams. The mechanisms for the superior alkaline stability and 99TcO4- capture performances of CPN-3 are investigated through combined experimental and computational studies. This work suggests an alternative perspective for designing functional materials to address nuclear waste management.

4f/5d Hybridization Induced Single-Electron Delocalization in an Azide-Bridged Dicerium Complex.

Dilanthanide complexes with one-electron delocalization are important targets for understanding the specific 4f/5d-bonding feature in lanthanide chemistry. Here, we report an isolable azide-bridged dicerium complex 3 [{(TrapenTMS)Ce}2(µ-N3)]• [Trapen = tris (2-aminobenzyl)amine; TMS = SiMe3], which is synthesized by the reaction of tripodal ligand-supported (TrapenTMS)CeIVCl complex 2 with NaN3. The structure and bonding nature of 3 are fully characterized by X-ray crystal diffraction analysis, electron paramagnetic resonance (EPR), magnetic measurement, cyclic voltammetry, X-ray absorption spectroscopy, and quantum-theoretical studies. Complex 3 presents a trans-bent central Ce-N3-Ce unit with a single electron of two mixed-valent Ce atoms. The unique low-temperature (2 K) anisotropic EPR signals [g = 1.135, 2.003, and 3.034] of 3 indicate that its spin density is distributed on the central Ce-N3-Ce unit with marked electron delocalization. Quantum chemical analyses show strong 4f/5d orbital mixing in the singly occupied molecular orbital of 3, which allows for the unpaired electron to extend throughout the cerium-azide-cerium unit via a multicentered one-electron (Ce-N3-Ce) interaction. This work extends the family of mixed-valent dilanthanide complexes and provides a paradigm for understanding the bonding motif of ligand-bridged dilanthanide complexes.

Regulating the Electronic Structure of MAX Phases Based on Rare Earth Element Sc to Enhance Electromagnetic Wave Absorption.

MAX phases are highly promising materials for electromagnetic (EM) wave absorption because of their specific combination of metal and ceramic properties, making them particularly suitable for harsh environments. However, their higher matching thickness and impedance mismatching can limit their ability to attenuate EM waves. To address this issue, researchers have focused on regulating the electronic structure of MAX phases through structural engineering. In this study, we successfully synthesized a ternary MAX phase known as Sc2GaC MAX with the rare earth element Sc incorporated into the M-site sublayer, resulting in exceptional conductivity and impressive stability at high temperatures. The Sc2GaC demonstrates a strong reflection loss (RL) of -47.7 dB (1.3 mm) and an effective absorption bandwidth (EAB) of 5.28 GHz. It also achieves effective absorption of EM wave energy across a wide frequency range, encompassing the X and Ku bands. This exceptional performance is observed within a thickness range of 1.3 to 2.1 mm, making it significantly superior to other Ga-MAX phases. Furthermore, Sc2GaC exhibited excellent absorption performance even at elevated temperatures. After undergoing oxidation at 800 °C, it achieves a minimum RL of -28.3 dB. Conversely, when treated at 1400 °C under an argon atmosphere, Sc2GaC demonstrates even higher performance, with a minimum RL of -46.1 dB. This study highlights the potential of structural engineering to modify the EM wave absorption performance of the MAX phase by controlling its intrinsic electronic structure.

Isotope Effect-Enabled Crystal Enlargement in Metal-Organic Frameworks.

Synthesizing large metal-organic framework (MOF) single crystals has garnered significant research interest, although it is hindered by the fast nucleation kinetics that gives rise to numerous small nuclei. Given the different chemical origins inherent in various types of MOFs, the development of a general approach to enhancing their crystal sizes presents a formidable challenge. Here, we propose a simple isotopic substitution strategy to promote size growth in MOFs by inhibiting nucleation, resulting in a substantial increase in the crystal volume ranging from 1.7- to 165-fold. Impressively, the crystals prepared under optimized conditions by normal approaches can be further enlarged by the isotope effect, yielding the largest MOF single crystal (2.9 cm × 0.48 cm × 0.23 cm) among the one-pot synthesis method. Detailed in situ characterizations reveal that the isotope effect can retard crystallization kinetics, establish a higher nucleation energy barrier, and consequently generate fewer nuclei that eventually grow larger. Compared with the smaller crystals, the isotope effect-enlarged crystal shows 33% improvement in the X-ray dose rate detection limit. This work enriches the understanding of the isotope effect on regulating the crystallization process and provides inspiration for exploring potential applications of large MOF single crystals.

Hydrogen Isotope Effect Endows a Breakthrough in Photoluminescent Covalent Organic Frameworks.

Luminescent covalent organic frameworks (LCOFs) have emerged as indispensable candidates in various applications due to their greater tunable emitting properties and structural robustness compared to small molecule emitters. An unsolved issue in this area is developing highly luminescent LCOFs of which the nonradiative quenching pathways were suppressed as much as possible. Here, a robust aminal-linked COF (DD-COF) possessing perdeuterated light-emitting monomers was designed and synthesized. The solid-state photoluminescence quantum yield of the DD-COF reaches 81%, significantly outcompeting all state-of-the-art LCOFs reported so far. The exceptional luminescent efficiency is attributed to the inhibition of different pathways of nonradiative decay, especially from bond vibrations where only substitution by a heavier isotope with a lower zero-point vibration frequency works. Furthermore, the prepared deuterated COF not only boosts higher photostability under UV irradiation but also enables superior fluorescence sensing performance for iodine detection compared to nondeuterated COF.

A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains.

Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary exposure to Hg. Here we report a hidden pathway of MeHg demethylation independent of light and microorganisms in rice plants. This natural pathway is driven by reactive oxygen species generated in vivo, rapidly transforming MeHg to inorganic Hg and then eliminating Hg from plants as gaseous Hg°. MeHg concentrations in rice grains would increase by 2.4- to 4.7-fold without this pathway, which equates to intelligence quotient losses of 0.01-0.51 points per newborn in major rice-consuming countries, corresponding to annual economic losses of US$30.7-84.2 billion globally. This discovered pathway effectively removes Hg from human food webs, playing an important role in exposure mitigation and global Hg cycling.

Recognition of Actinides by Siderocalin.

Plain simulations and enhanced sampling unveil a novel siderocalin (Scn) recognition mode for An-Ent (where An = actinides and Ent = enterobactin) complexes and identify a "seesaw" relationship between actinide affinity to Ent and Scn recognition to an An-Ent complex. Electrostatic interactions predominantly govern competitive binding in both processes. Additionally, hydrolysis-induced negative charge, water expulsion-driven entropy, and Ent's conformational adaptability collectively enhance high-affinity recognition.

An Aryl-ether-linked Covalent Organic Framework Modified with Thioamide Groups for Selective Extraction of Palladium from Strong Acid Solutions.

Efficient adsorption of palladium ions from acid nuclear waste solution is crucial for ensuring the safety of vitrification process for radioactive waste. However, the limited stability and selectivity of most current adsorbents hinder their practical applications under strong acid and intense radiation conditions. Herein, to address these limitations, we designed and synthesized an aryl-ether-linked covalent organic framework (COF-316-DM) grafted dimethylthiocarbamoyl groups on the pore walls. This unique structure endows COF-316-DM with high stability and exceptional palladium capture capacity. The robust polyarylether linkage enables COF-316-DM to withstand irradiation doses of 200 or 400 kGy of ß/γ ray. Furthermore, COF-316-DM demonstrates fast adsorption kinetics, high adsorption capacity (147 mg g-1 ), and excellent reusability in 4 M nitric acid. Moreover, COF-316-DM exhibits remarkable selectivity for palladium ions in the presence of 17 interference ions, simulating high level liquid waste scenario. The superior adsorption performance can be attributed to the strong binding affinity between the thioamide groups and Pd2+ ions, as confirmed by the comprehensive analysis of FT-IR and XPS spectra. Our findings highlight the potential of COFs with robust linkers and tailored functional groups for efficient and selective capture of metal ions, even in harsh environmental conditions.

Manipulation of Shallow-Trap States in Halide Double Perovskite Enables Real-Time Radiation Dosimetry.

Storage phosphors displaying defect emissions are indispensable in technologically advanced radiation dosimeters. The current dosimeter is limited to the passive detection mode, where ionizing radiation-induced deep-trap defects must be activated by external stimulation such as light or heat. Herein, we designed a new type of shallow-trap storage phosphor by controlling the dopant amounts of Ag+ and Bi3+ in the host lattice of Cs2NaInCl6. A distinct phenomenon of X-ray-induced emission (XIE) is observed for the first time in an intrinsically nonemissive perovskite. The intensity of XIE exhibits a quantitative relationship with the accumulated dose, enabling a real-time radiation dosimeter. Thermoluminescence and in situ X-ray photoelectron spectroscopy verify that the emission originates from the radiative recombination of electrons and holes associated with X-ray-induced traps. Theoretical calculations reveal the evolution process of Cl-Cl dimers serving as hole trap states. Analysis of temperature-dependent radioluminescence spectra provides evidence that the intrinsic electron-phonon interaction in 0.005 Ag+@ Cs2NaInCl6 is significantly reduced under X-ray irradiation. Moreover, 0.025 Bi3+@ Cs2NaInCl6 shows an elevated sensitivity to the accumulated dose with a broad response range from 0.08 to 45.05 Gy. This work discloses defect manipulation in halide double perovskites, giving rise to distinct shallow-trap storage phosphors that bridge traditional deep-trap storage phosphors and scintillators and enabling a brand-new type of material for real-time radiation dosimetry.

Radiation-Induced De Novo Defects in Metal-Organic Frameworks Boost CO2 Sorption.

Defects in metal-organic frameworks (MOFs) can significantly change their local microstructures, thus notably leading to an alteration-induced performance in sorption or catalysis. However, achieving de novo defect engineering in MOFs under ambient conditions without the scarification of their crystallinity remains a challenge. Herein, we successfully synthesize defective ZIF-7 through 60Co gamma ray radiation under ambient conditions. The obtained ZIF-7 is defect-rich but also has excellent crystallinity, enhanced BET surface area, and hierarchical pore structure. Moreover, the amount and structure of these defects within ZIF-7 were determined from the two-dimensional (2D) 13C-1H frequency-switched Lee-Goldburg heteronuclear correlation (FSLG-HETCOR) spectra, continuous rotation electron diffraction (cRED), and high-resolution transmission electron microscopy (HRTEM). Interestingly, the defects in ZIF-7 all strongly bind to CO2, leading to a remarkable enhancement of the CO2 sorption capability compared with that synthesized by the solvothermal method.

Unveiling the Reduction Mechanism of Pu(IV) by Acetaldoxime.

The separation of plutonium (Pu) from spent nuclear fuel was achieved by effectively adjusting the oxidation state of Pu from +IV to +III in the plutonium uranium reduction extraction (PUREX) process. Acetaldoxime (CH3CHNOH) as a free salt reductant can rapidly reduce Pu(IV), but the reduction mechanism remains indistinct. Herein, we explore the reduction mechanism of two Pu(IV) ions by one CH3CHNOH molecule, where the second Pu(IV) reduction is the rate-determining step with the energy barrier of 19.24 kcal mol-1, which is in line with the experimental activation energy (20.95 ± 2.34 kcal mol-1). Additionally, the results of structure and spin density analyses demonstrate that the first and second Pu(IV) reduction is attributed to hydrogen atom transfer and hydroxyl ligand transfer, respectively. Analysis of localized molecular orbitals unveils that the reduction process is accompanied by the breaking of the Pu-OOH bond and the formation of the OOH-H and C-OOH bonds. The reaction energies confirm that the reduction of Pu(IV) by acetaldoxime is both thermodynamically and kinetically accessible. In this work, we elucidate the reduction mechanism of Pu(IV) with CH3CHNOH, which provides a theoretical understanding of the rapid reduction of Pu(IV).

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.

Th6-Based Multicomponent Heterometallic Metal-Organic Frameworks Featuring 6,12-Connected Topology for Iodine Adsorption.

Its high coordination number and tendency to cluster make Th4+ suitable for constructing metal-organic frameworks (MOFs) with novel topologies. In this work, two novel thorium-based heterometallic MOF isomers (IHEP-17 and IHEP-18) were assembled from a Th6 cluster, a multifunctional organic ligand [4-(1H-pyrazol-4-yl)benzoic acid (HPyba)], and Cu2+/Ni2+ cations via the one-pot solvothermal synthesis strategy. The framework features a 6,12-connected new topology net and contains two kinds of supramolecular cage structures, Th36M4 and Th24M2, suitable for guest exchange. Both MOF materials can efficiently adsorb I2. X-ray photoelectron spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction indicate that the adsorbed iodine is uniformly distributed within the Th36M4 cage but not the Th24M2 cage in the form of I3-.

Thermally Induced Orderly Alignment of Porphyrin Photoactive Motifs in Metal-Organic Frameworks for Boosting Photocatalytic CO2 Reduction.

Efficient transfer of charge carriers through a fast transport pathway is crucial to excellent photocatalytic reduction performance in solar-driven CO2 reduction, but it is still challenging to effectively modulate the electronic transport pathway between photoactive motifs by feasible chemical means. In this work, we propose a thermally induced strategy to precisely modulate the fast electron transport pathway formed between the photoactive motifs of a porphyrin metal-organic framework using thorium ion with large ionic radius and high coordination number as the coordination-labile metal node. As a result, the stacking pattern of porphyrin molecules in the framework before and after the crystal transformations has changed dramatically, which leads to significant differences in the separation efficiency of photogenerated carriers in MOFs. The rate of photocatalytic reduction of CO2 to CO by IHEP-22(Co) reaches 350.9 µmol·h-1·g-1, which is 3.60 times that of IHEP-21(Co) and 1.46 times that of IHEP-23(Co). Photoelectrochemical characterizations and theoretical calculations suggest that the electron transport channels formed between porphyrin molecules inhibit the recombination of photogenerated carriers, resulting in high performance for photocatalytic CO2 reduction. The interaction mechanism of CO2 with IHEP-22(Co) was clarified by using in-situ electron paramagnetic resonance, in-situ diffuse reflectance infrared Fourier transform spectroscopy, in-situ extended X-ray absorption fine structure spectroscopy, and theoretical calculations. These results provide a new method to regulate the efficient separation and migration of charge carriers in CO2 reduction photocatalysts and will be helpful to guide the design and synthesis of photocatalysts with superior performance for the production of solar fuels.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

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