Rapid Destruction of Two Types of Chemical Warfare Agent Simulants by Hybrid Polyoxomolybdates Modified by Carboxylic Acid Ligands

Nb(V)-containing saponite: A versatile clay for the catalytic degradation of the hazardous organophosphorus pesticide paraoxon under very mild conditions

A synthetic saponite clay containing structural Nb(V) metal centres (NbSAP) was investigated in the abatement of paraoxon-ethyl, an anti-cholinergic organophosphorus pesticide, under mild conditions (neutral pH, room temperature and ambient pressure) in heterogenous phase, without additional basic additives. The material was selected according to its high surface acidity and ease of preparation through a one-step hydrothermal synthesis. The presence of Nb(V) ions played a crucial role in efficiently catalysing the degradation of aggressive chemical substrates. A niobium(V) oxide with very low surface acidity was also tested as a reference material. The study employed a multi-technique approach to monitor the pesticide degradation pathway and by-products formed during abatement experiments in polar non-protic and aqueous solvents. Notably, in water, the concentration of paraoxon-ethyl significantly decreased by 82 % within the first hour of contact with the clay. Additionally, NbSAP demonstrated a good performance after three repeated catalytic cycles and subsequent reactivation.

Se-Rich Multinuclear Er-Containing Dawson-type Poly(selenotungstate)

A multinuclear Er-containing Dawson-type poly(selenotungstate) (poly(ST)) [H2N(CH3)2]12Na8Cs6H26 [Er12Se14W12O72(H2O)6(Se2W14O52)6]·78H2O (1) was made by the one-pot assembly with an excess SeO32- source in the reaction system. The polyoxoanion consists of an extremely rare Er12Se14W12O72(H2O)6 ({Er12Se14W12}) cluster core surrounded by six tetravacant Dawson-type Se2W14O52 ({Se2W14}) fragments, representing the most Se-containing Dawson-type structure so far. Notably, the {Er12Se14W12} cluster exhibits an interesting trefoil-shaped configuration, formed by the condensation of a central Er3Se2O6 ({Er3Se2}) cage with three Er3Se4W4O22(H2O)2 ({Er3Se4W4}) clusters. The catalytic performance of 1 was evaluated by the oxidative decontamination of 2-chloroethyl ethyl sulfide (CEES) into nontoxic 2-chloroethyl ethyl sulfoxide (CEESO), showing remarkable conversion and selectivity, as well as excellent reusability.

Exclusive generation of a superoxide radical by a porous aromatic framework for fast photocatalytic decontamination of mustard gas simulant in room air

Mustard gas and other chemical warfare agents (CWAs) are a global threat to public security, arising from unpredictable emergencies and chemical spill accidents. So far, photocatalysts such as metal clusters, polyoxometalates and porous solids have been exploited for oxidative degradation of mustard gas, commonly with 1O2 as reactive species. However, the production of 1O2 is oxygen-dependent and requires a high oxygen concentration to sustain the detoxication process. For safety and operation process considerations, it is always preferable to rapidly detoxify dangerous chemicals in the atmosphere of room air. In this work, a porous aromatic framework, PAF-68, was synthesized as a metal-free photocatalyst. In the presence of PAF-68, fast detoxication occurred in typical room air atmosphere. The half-life (t 1/2) for the complete conversion of mustard gas simulant to nontoxic product in room air was only 1.7 min, which is comparable to the performance in pure oxygen, surpassing that of any other porous photocatalysts. It was found that ˙O2 - rather than 1O2 is the predominant reactive species initiated by PAF-68 for mustard gas detoxication. Unlike the formation of 1O2 which prefers the environment of pure oxygen, generation of the ˙O2 - is an oxygen-independent process. It is suggested that amorphous PAFs possess low exciton binding energy and long decay lifetime, which facilitate the generation of ˙O2 -, and this offers a general design strategy to detoxifying chemical warfare agents under real-world conditions.

{SeO2(OH)} Bridging Lanthanide-Containing Antimono-Seleno-Tungstates

A series of new trigonal pyramidal {SeO2(OH)} bridging lanthanide-containing antimono-seleno-tungstates [H2N(CH3)2]8Na8Cs4H9[Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]2·32H2O [Ln = Tb (1), Dy (2), Ho (3), Er (4)] have been prepared by the synthetic strategy of simultaneously using the antimonotungstate precursor and simple material in an acidic aqueous solution and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectrometry, and thermogravimetric analysis. Their molecular structures contain an unprecedented hexameric polyoxoanion [Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]229- constituted by two equivalent trimeric subunits Ln2W4O9(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33) bridged via two μ2-{SeO2(OH)} linkers. Furthermore, the catalytic oxidation of various aromatic sulfides and sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) by compound 3 as the heterogeneous catalyst has been investigated, exhibiting high conversion and selectivity as well as good stability and recyclability.

Exploring Electron Transfer Mechanism in Synergistic Interactional Reduced Polyoxometalate-Based Cu(I)-Organic Framework for Photocatalytic Removal of U(VI)

Photocatalytic reduction of U(VI) is a promising method for removing uranium containing pollutants. However, using polyoxometalate-based metal-organic frameworks (POMOFs) for photoreduction of U(VI) is rare, and the relevant charge transfer pathway is also not yet clear. In this article, we demonstrate a highly efficient strategy and revealed a clearly electron transfer pathway for the photoreduction of U(VI) with 99% removal efficiency by using a novel POMOF, [Cu(4,4'-bipy)]5·{AsMo4VMo6VIV2VO40(VIVO)[VIVO(H2O)]}·2H2O (1), as catalyst. The POMOF catalyst was constructed by the connection of reduced {AsMo10V4} clusters and Cu(I)-MOF chains through Cu-O coordination bonds, which exhibits a broader and stronger light absorption capacity due to the presence of reduced {AsMo10V4} clusters. Significantly, the transition of electrons from Cu(I)-MOF to {AsMo10V4} clusters (Cu → Mo/V) greatly inhibits the recombination of photogenerated carriers, thereby advancing electron transfer. More importantly, the {AsMo10V4} clusters are not only adsorption sites but also catalytically active sites. This causes the fast transfer of photogenerated electrons from Mo/V to UO22+(Mo/V → O → U) via the surface oxygen atoms. The shorter electron transmission distance between catalytic active sites and UO22+ achieves faster and more effective electron transport. All in all, the highly effective photocatalytic removal of U(VI) using the POMOF as a catalyst is predominantly due to the synergistic interaction between Cu(I)-MOFs and reduced {AsMo10V4} clusters.

Rapid Oxidative Detoxification of Mustard Simulant by the Multisite Synergistic Catalytic Action of {PMoVI11MoVO40CuI8} Units

Under hydrothermal and solvent-thermal conditions, we synthesized two novel polyoxometalate (POM)-based hybrids: [CuI4(Pz)2(H2O)8(PMoVI11MoVO40)]·3.5H2O (1, Pz = pyrazine) and [(C2H8N)5(HPMoVI9MoV3O40)]·DMF·4H2O (2). Single-crystal X-ray diffraction indicates that compound 1 is a three-dimensional structure consisting of Cu (I), {PMo12} anions, Pz, and water, where Cu (I) can be considered as Lewis acid sites. Furthermore, both compounds 1 and 2 possess favorable catalysis activity in catalyzing the conversion of chemical warfare agent simulant 2-chloroethylethyl sulfide (CEES) to nontoxic production of 2-chloroethylethyl sulfoxide (CEESO) under ambient temperature. Significantly, 1 could realize 98% conversion and 100% selectivity of CEES owing to the multisite synergy in the {PMoVI11MoVO40CuI8} units in which the tricoordinated Cu (I) could interact with S and O atoms from CEES and H2O2, respectively. This interaction not only decreases the distance of CEES from peroxomolybdenum species formed by H2O2 but also activates CEES.

Metal-Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal-organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal-ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes.

Iron doped BiOBr loaded on carbon spheres for improved visible-light-driven detoxification of 2-chloroethyl sulfide

In this study, flower-like porous iron doped bismuth oxybromide on porous activated carbon visible light catalysts (BiOBr/Fe@AC) were prepared by a reactive imidazole ionic liquid surfactant assisted solvothermal process. The morphologies, structures, optical properties and photocatalytic properties were investigated in detail. The morphology of the synthesized Fe doped BiOBr composites gradually changed from a regular spherical shape to a non-specific shape with the increase of the alkyl chain length of the ionic liquid surfactants. The photocurrent of BiOBr/Fe@AC composites is greatly influenced by the content of Fe, the type of carbon sphere and the size of the composites. The photocatalytic activity of the obtained BiOBr/Fe@AC composites was evaluated by the degradation of 2-chloroethyl sulfide (CEES) under visible light. The BiOBr/Fe@AC composites exhibited significantly enhanced photocatalytic performance compared to that of pure BiOBr and the 10.0% Fe doped BiOBr/Fe@AC composite displayed the highest photocatalytic activity. The main active species were determined to be holes and superoxide radicals by electron spin resonance (ESR) analysis and free radical trapping experiments. The introduction of iron can improve the separation and transfer rate of photoinduced charges. Carbon spheres can enhance light harvesting, improve electron transfer and increase the number of catalytic active sites. Iron and carbon embellishment is an effective strategy to enhance the photocatalytic efficiency of BiOBr. Finally, a possible photocatalytic mechanism of BiOBr/Fe@AC has been proposed.

A Zr-added Dawson-type poly(polyoxometalate)

A novel Zr-added trimer, [H₂N(CH₃)₂]₁₀H₁₄[(Zr₂P₂W₁₆O₆₁)₃]·7H₂O (1), has been made under hydrothermal conditions, and contains the highest number of Zr centers in known Dawson-type poly(POM)s. A remarkable feature of this study is the first discovery of a new type of divacant [α-5,10-P₂W₁₆O₆₀]^14- fragment, which assembles with Zr⁴⁺ ions to form a cyclic trimer. Furthermore, 1 as a heterogeneous catalyst exhibits high activity for the selective oxidative degradation of a sulfur mustard simulant CEES.

Catalytic metal-organic framework-melamine foam composite as an efficient material for the elimination of organic pollutants

Water-insoluble organic pollutants in environment, such as sea oil spill, industrial reagents, and the abused organic pesticides, bring great risks to global water systems, which thus requires effective approaches for organic pollutant elimination. In this study, we report a catalytic metal-organic framework (MOF)-melamine foam (MF) composite material (DDT-UiO-66-NH₂@MF) showing excellent oil-water separation performance and enzyme-like degradation ability toward organophosphorus pesticides. The fabrication of DDT-UiO-66-NH₂@MF is based on the immobilization of a MOF-derived nanozyme (UiO-66-NH₂) on MF sponge, and followed by the hydrophobic modification of UiO-66-NH₂ by 1-dodecanethiol (DDT). The obtained DDT-UiO-66-NH₂@MF thus displayed superhydrophobic/superhydrophilic property with a high water contact angle (WCA = 144.6°) and specific adsorption capacity toward various oils/organic solvents (62.2-119.8 g/g), which leads to a continuous oil-water separation on a simple device. In the meanwhile, owing to the enzyme-like property of UiO-66-NH₂, DDT-UiO-66-NH₂@MF also displayed good ability to hydrolyze paraoxon under mild conditions, which facilitates the elimination of toxic pesticide residuals in water systems. This work provides a simple, efficient, and green approach for the separation and treatment of water-insoluble organic pollutants, as well as expands the use of MOFs-MF sponge composite materials in environmental sustainability.

Polyoxovanadate-Based Cyclomatrix Polyphosphazene Microspheres as Efficient Heterogeneous Catalysts for the Selective Oxidation and Desulfurization of Sulfides

The [V₆O₁₃]^2- cluster is successfully immobilized to the polymeric framework of cyclomatrix polyphosphazene via the facile precipitation polymerization between the phenol group symmetrically modified [V₆O₁₃]^2- and hexachlorocyclotriphosphazene. The structure of the as-prepared polyoxometalate-containing polyphosphazene (HCCP-V) was characterized by FT-IR, XPS, TGA, BET, as well as SEM and zeta potential. The presence of a rigid polyoxometalate cluster not only supports the porous structure of the polymeric framework but also provides an improved catalytic oxidation property. By using H₂O₂ as an oxidant, the as-prepared HCCP-V exhibited improved catalytic oxidation activity toward MPS, DBT, and CEES, which can achieve as high as 99% conversion. More importantly, the immobilization of POMs in the network of cyclomatrix polyphosphazene also provides better recyclability and stability of the heterogeneous catalyst.

Highly Reactive Heterogeneous Nanofibers Catalyst Based on [Mo154] Clusters for Green Aerobic Oxidation of Sulfur Mustard Analogues under Ambient Conditions

BACKGROUND

Due to the increasing chemical and biological threats posed by terrorist attacks, there is a need to design and prepare nanofibers (NFs) with the ability to neutralize CWAs. For this purpose polyacrylonitrile NFs and polyoxomolybdate [Mo154] (abbreviated as PAN NFs/[Mo154]) as a heterogeneous catalyst was prepared by electrospinning method with a diameter of about 100nm.

OBJECTIVE

The PAN NFs/[Mo154] catalyze the selective aerobic oxidation of sulfur mustard stimulants, such as 2-chloroethyl ethyl sulfide (2-CEES) and 2-chloroethyl phenyl sulfide (2-CEPS) under green and "ambient" conditions (25◦C, 1atm O2) in presence of ethanol with high efficiency and selectivity. 2-CEES was selected as a model reaction to optimize the parameters of the reaction.

METHOD

The progress of the reaction was evaluated after different times using GC-FID, GC-MS and TLC. The reaction product was also confirmed by 1H-NMR spectroscopy.

RESULT

The aerobic oxidation results of 2-CEES showed that PAN NFs/[Mo154] have a conversion of 98% to produce only a nontoxic product, 2-CEESO with selectivity of 100% after 45min. The results were performed using [Mo154] without any PAN NFs for comparison. Whereas [Mo154] converts only 52% of 2-CEES under the identical conditions.

CONCLUSION

Heterogeneous PAN NFs/[Mo154] catalyst was reused after washing with solvent up to 5 steps without leaching of [Mo154] from PAN NFs and without any loss in efficiency due to the morphology of NFs. In addition to the recovery of PAN NFs/[Mo154] in different cycles, the use of FT-IR, UV-Vis and TEM techniques confirms the stability and morphology of PAN NFs/[Mo154] after the fifth cycle, 2-CEES oxidation. According to our information, this report is the first use of PAN NFs enriched with [Mo154] for aerobic oxidation of sulfur mustard simulants.

Synthesis of a UiO-66/g-C3N4 composite using terephthalic acid obtained from waste plastic for the photocatalytic degradation of the chemical warfare agent simulant, methyl paraoxon

In our study, Zr-based UiO-66 (Zr) was synthesized using terephthalic acid obtained from waste plastic. Thereafter, UiO-66/g-C₃N₄ composites were prepared by the solvothermal method, and their photocatalytic activity in the photodegradation of the chemical warfare agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), was evaluated. The as-synthesized UiO-66/g-C₃N₄ exhibited a high surface area (1440 m² g⁻¹) and a high capillary volume (1.49 cm³ g⁻¹). The UiO-66/g-C₃N₄ samples absorbed a visible light band with bandgap energies of 2.13–2.88 eV. The as-synthesized UiO-66/g-C₃N₄ composites exhibited highly efficient degradation of DMNP with a short half-life (t_1/2 of 2.17 min) at pH 7 under visible light irradiation. The trapping experiments confirmed that the h⁺ and ˙O₂⁻ radicals played an important role in the photocatalytic degradation of DMNP. The UiO-66/g-C₃N₄ catalyst simultaneously performed two processes: the hydrolysis and photocatalytic oxidation of DMNP in water. During irradiation, a p–n heterojunction between UiO-66 and g-C₃N₄ restricted the recombination of photogenerated electrons and holes, resulting in the enhancement in the degradation rate of DMNP.

UiO-66/g-C₃N₄ with a high surface area (1440 m² g⁻¹) and a high capillary volume (1.49 cm³ g⁻¹) exhibited highly efficient degradation of dimethyl 4-nitrophenyl phosphate with t_1/2 = 2.17 min.

Nanoflake-Engineered Zirconic Fibrous Aerogels with Parallel-Arrayed Conduits for Fast Nerve Agent Degradation

Chemical warfare agents (CWAs) pose huge threats to ecological environments, agriculture, and human health due to the turbulent international situation in contemporary society. Zirconium hydroxide (Zr(OH)₄) has captured the prime focus as an effective candidate for CWA decomposition but is often hindered by the isolated powder form. Here, we demonstrate a scalable three-dimensional space-confined synthetic strategy to fabricate nanoflake-engineered zirconic fibrous aerogels (NZFAs). Our strategy enables the stereoscopic Zr(OH)₄ nanoflakes vertically and evenly in situ grown on the interconnected fibrous framework, remarkably enlarging the surface area and providing rich active sites for CWA catalysis. The as-synthesized NZFAs exhibit intriguing properties of ultralow density (>0.37 mg cm^-3), shape-memory behavior under 90% strain, and robust fatigue resistance over 10⁶ compression cycles at 40% strain. Meanwhile, the high air permeability, prominent adsorptivity, and reusability make them state-of-the-art chemical protective materials. This work may provide an avenue for developing next-generation aerogel-based catalysts and beyond.

Highly Efficient Synthesis of p-Benzoquinones Catalyzed by Robust Two-Dimensional POM-Based Coordination Polymers

Selective oxidation of alkyl-substituted phenols offers efficient access to p-benzoquinones (BQs) that serve as key components for synthesizing biologically active compounds, but rational manufacture of efficient recyclable catalysts for such a reaction remains a severe challenge. Herein, two crystalline 2D polyoxometalate-based coordination polymers (POMCPs), formulated as H₃[Cu^I₃(L)₃]₂[PM₁₂O₄₀]·xH₂O (M = Mo, x = 4 for 1; M = W, x = 6 for 2; and HL = 4-(1H-tetazol-5-yl)pyridine), are prepared by a mineralizer-assisted one-step synthesis strategy and explored as heterogeneous catalysts for p-BQs synthesis. Both compounds have been characterized through elemental analysis, EDS analysis, infrared spectroscopy, UV-vis diffuse reflectance spectrum, EPR, XPS, BET, single-crystal, and powder X-ray diffraction. Single-crystal X-ray diffraction analysis indicates that both 1 and 2 exhibit an interesting 2D sheet structure composed of 2-connected Keggin type anions [PM₁₂O₄₀]^3- and hexa-nuclear {Cu^I₆(HL)₆} cluster-based metal-organic chains via Cu···O interactions. When used as catalysts, POMCPs 1 and 2 have excellent catalytic activities in the selective oxidation of substituted phenols to p-BQs with H₂O₂. Notedly, in the model reaction from 2,3,6-trimethylphenol (TMP) to the vitamin E key intermediate trimethyl-p-benzoquinone (TMBQ), the catalytic activities expressed by turnover frequency (TOF) of 1 and 2 can reach an unprecedented 2400 and 2000 h^-1, respectively, at close to 100% TMBQ yield. The truly heterogeneous nature, stability, and structural integrity of both catalysts were ascertained by FTIR, PXRD techniques, and the following cycles. Mechanism studies reveal that both catalysts can involve a dual reaction pathway through a heterolytic oxygen atom transfer mechanism and homolytic radical mechanism. Moreover, the 2D POMCPs with highly accessible bilateral active sites and efficient mass transfer efficiency possess superior catalytic performance to their analogous 3D species.

Mono- and Di-Sc-Substituted Keggin Polyoxometalates: Effective Lewis Acid Catalysts for Nerve Agent Simulant Hydrolysis and Mechanistic Insights

Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K₄[Sc(H₂O)PW₁₁O₃₉]·22H₂O·2(CH₃COOK) (1) and di-Sc-substituted Na₇[Sc₂(CH₃COO)₂PW₁₀O₃₈]·10H₂O·2CH₃COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by ³¹P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97%) is much better than that of 1 (conversion: 28%). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (¹³C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.

Photothermal graphene/UiO-66-NH2 fabrics for ultrafast catalytic degradation of chemical warfare agent simulants

Lightweight and wearable fabrics with rapid self-detoxification functions are highly desired to resist chemical warfare agents (CWAs). Metal organic frameworks (MOFs) with high specific surface area and customizability are singularly attractive because of their ability to effectively capture and catalytically degrade CWAs. Herein, photothermal graphene-based nanocomposite fabrics are designed by wet-spinning and chemical reduction of graphene oxide fibers followed by in situ growth of UiO-66-NH₂. The flexible graphene fabrics decorated with UiO-66-NH₂ nanoparticles exhibit an ultrafast photothermal catalytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a typical simulant of CWAs. The half-life of the degradation reaction decreases from 3.4 to 1.6 min under simulated solar light irradiation, a significant gain over the values reported in the literature. Furthermore, DMNP can be degraded in 20 min by the graphene/UiO-66-NH₂ fabric, and even after 5 cycles the degradation efficiency still retains more than 92 %. More importantly, the photothermal conversion of graphene and its instantaneous heat transfer to the UiO-66-NH₂ catalyst effectively accelerate the catalytic reaction kinetics, achieving the fast detoxification of DMNP. The combination of catalytic degradation of MOFs with photothermal conversion effect of graphene makes the lightweight and flexible fabrics promising for protection against CWAs and other pollutants.

A dual-function all-inorganic intercluster salt comprising the polycation ε-[Al13O4(OH)24(H2O)12]7+ and polyanion α-[PMo10V2O40]5- for detoxifying sulfur mustard and soman

ε-[Al13O4(OH)24(H2O)12]7+, which shares similarity with the phosphotriesterase active site ZnII-OH-ZnII, was specially chosen to interact with the cluster α-PMo10V2O405- to form a new three-dimensional intercluster, which crystallized in the monoclinic space group P21/m with Z = 2, for the decontamination of chemical warfare agents. The experimental results showed that 50 mg of the compound decontaminated 96.4% (within 120 min) and 99.5% (within 40 min) of sulfur mustard (HD) (4 μL) and soman (GD) (4 μL), respectively, in ambient conditions. The decontamination processes followed first-order reaction kinetics with a rate constant and half-life of 0.01234 min-1 and 56.15 min for HD and 0.1198 min-1 and 5.78 min for GD, respectively. It was concluded that the α-PMo10V2O405- moiety was responsible for the catalytic oxidation of HD into non-toxic sulfoxide, while the ε-[Al13O4(OH)24(H2O)12]7+ moiety was responsible for the catalytic hydrolysis of HD and GD into nontoxic hydrolysates. Besides, the compound showed notable efficacy for the decontamination of HD on guinea pig skin and of GD on Kunming mouse skin, indicating high potential for use in human skin protection and treatment.

Multimodal Characterization of Materials and Decontamination Processes for Chemical Warfare Protection

This Review summarizes the recent progress made in the field of chemical threat reduction by utilizing new in situ analytical techniques and combinations thereof to study multifunctional materials designed for capture and decomposition of nerve gases and their simulants. The emphasis is on the use of in situ experiments that simulate realistic operating conditions (solid-gas interface, ambient pressures and temperatures, time-resolved measurements) and advanced synchrotron methods, such as in situ X-ray absorption and scattering methods, a combination thereof with other complementary measurements (e.g., XPS, Raman, DRIFTS, NMR), and theoretical modeling. The examples presented in this Review range from studies of the adsorption and decomposition of nerve agents and their simulants on Zr-based metal organic frameworks to Nb and Zr-based polyoxometalates and metal (hydro)oxide materials. The approaches employed in these studies ultimately demonstrate how advanced synchrotron-based in situ X-ray absorption spectroscopy and diffraction can be exploited to develop an atomic- level understanding of interfacial binding and reaction of chemical warfare agents, which impacts the development of novel filtration media and other protective materials.

Metal-Organic Framework- and Polyoxometalate-Based Sorbents for the Uptake and Destruction of Chemical Warfare Agents

The threat of chemical warfare agents (CWAs), assured by their ease of synthesis and effectiveness as a terrorizing weapon, will persist long after the once-tremendous stockpiles in the U.S. and elsewhere are finally destroyed. As such, soldier and civilian protection, battlefield decontamination, and environmental remediation from CWAs remain top national security priorities. New chemical approaches for the fast and complete destruction of CWAs have been an active field of research for many decades, and new technologies have generated immense interest. In particular, our research team and others have shown metal-organic frameworks (MOFs) and polyoxometalates (POMs) to be active for sequestering CWAs and even catalyzing the rapid hydrolysis of agents. In this Forum Article, we highlight recent advancements made in the understanding and evaluation of POMs and Zr-based MOFs as CWA decontamination materials. Specifically, our aim is to bridge the gap between controlled, solution-phase laboratory studies and real-world or battlefield-like conditions by examining agent-material interactions at the gas-solid interface utilizing a multimodal experimental and computational approach. Herein, we report our progress in addressing the following research goals: (1) elucidating molecular-level mechanisms of the adsorption, diffusion, and reaction of CWA and CWA simulants within a series of Zr-based MOFs, such as UiO-66, MOF-808, and NU-1000, and POMs, including Cs₈Nb₆O₁₉ and (Et₂NH₂)₈[(α-PW₁₁O₃₉Zr(μ-OH)(H₂O))₂]·7H₂O, (2) probing the effects that common ambient gases, such as CO₂, SO₂, and NO₂, have on the efficacy of the MOF and POM materials for CWA destruction, and (3) using CWA simulant results to develop hypotheses for live agent chemistry. Key hypotheses are then tested with targeted live agent studies. Overall, our collaborative effort has provided insight into the fundamental aspects of agent-material interactions and revealed strategies for new catalyst development.

Highly efficient oxidation of various thioethers catalyzed by organic ligand-modified polyoxomolybdates

Herein, four hybrid dimers based on the carboxylic acid ligand-modified polyoxomolybdates were prepared, which could rapidly and selectively oxidize various phenyl sulfides and the sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES).

Discovery of a New Family of Polyoxometalate-Based Hybrids with Improved Catalytic Performances for Selective Sulfoxidation: The Synergy between Classic Heptamolybdate Anions and Complex Cations

A series of functional cation-regulated isopolymolybdate-based organic-inorganic hybrid compounds, Na₂H₂[Mo₄O₁₂(C₈H₁₇O₅N)₂]·10H₂O (1), Na₂[M(Bis-tris)(H₂O)]₂[Mo₇O₂₄]·10H₂O [M = Cu, 2; Ni, 3; Co, 4; Zn, 5; Bis-tris = 2,2-Bis(hydroxymethyl)-2,2',2″-nitrilotriethanol], and (NH₄)₂[M(Bis-tris)(H₂O)]₂[Mo₇O₂₄]·6H₂O (M = Zn, 6; Cu, 7), were synthesized and characterized toward advanced molecular catalyst design. Compound 1 is a covalently bonded adduct, and its self-assembly process can be probed by electrospray ionization mass spectrometry (ESI-MS). Compounds 2-7 are polyoxometalate (POM)-based hybrids containing classic heptamolybdate anions and complex cations with Bis-tris ligands. All of these compounds showed remarkable catalytic effects for selective sulfide oxidation. To the best of our knowledge, compound 5 presents the best catalytic activity so far among the reported hybrid materials with common easily synthesized small-molecule POM clusters and also exhibits outstanding reliability. The conclusion of the catalytic effect is drawn from the results that Zn-based compounds have better catalytic effects than other transition-metal-containing compounds and the compound constructed by Na⁺ has higher catalytic activity than that constructed by NH₄⁺. The mechanism studies show that the improvements of the catalytic performance are caused by the synergy between classic heptamolybdate anions and complex cations. ESI-MS data and UV-vis spectra revealed that the POM anions can form intermediate peroxomolybdenum units during catalytic reaction. Further, the combination of the substrate thioanisole with complex cations was characterized by NMR experiments and UV-vis spectra. Thus, a new synergistic mechanism of anions and cations is proposed in which the activated thioanisole is used as a nucleophile to attack the peroxomolybdenum bonds, and this provides a new strategy in the design of reliable POM-based catalysts.

Multiunit Catalysts with Synergistic Reactivity: Three-Dimensional Polyoxometalate-Based Coordination Polymers for Highly Efficient Synthesis of Functionalized p-Benzoquinones

The rational design of highly efficient catalysts for the synthesis of functionalized p-benzoquinones (p-BQs) is of great significance for the manufacture of bioactive compounds. Herein, two 3D crystalline polyoxometalate-based coordination polymers (POMCPs) are used as heterogeneous catalysts for the synthesis of p-BQs, which are H[Cu^II(ttb)(H₂O)₃]₂[Cu^II(ttb)Cl]₂[PW₁₂O₄₀]·4H₂O (1) (Httb = 1-(tetrazol-5-yl)-4-(triazol-1-yl)benzene) and [ClCu₆^I(trz₎₄][ClCu₅^I(trz)₄]₂[Cu^II(H₂O)][PW₁₂O₄₀] (2) (trz = 1,2,4-triazole). Both compounds were characterized by elemental analysis, IR, XPS, solid diffuse reflective spectroscopy, TG analysis, and single-crystal X-ray diffraction. In 1, Keggin anions [PW₁₂O₄₀]^3- locate in 1D square channels constructed from wave-like Cu-ttb layers to form a 3D POMCP by coordinating to Cu ions, and in 2, [PW₁₂O₄₀]^3- anions situate in eight-membered Cu-trz channels via Cu···O interactions to yield a 3D POMCP structure. The catalytic activities of 1 and 2 have been evaluated in the selective oxidation of alkylphenols/alkoxybenzenes/methylnaphthalene, especially in the oxidation reaction of 2,3,6-trimethylphenol (TMP) to 2,3,5-trimethyl-p-benzoquinone (TMBQ, vitamin E key intermediate), with H₂O₂ as oxidant. By using catalysts 1 and 2 under optimal conditions, the yield of TMBQ can reach 99% and 96% within 10-20 min, respectively. Both catalysts demonstrated high turnover frequencies (300 h^-1 for 1 and 600 h^-1 for 2) and the truly heterogeneous nature. 1 and 2 catalyzed the synthesis of p-BQs on the basis of effective cooperative catalytic activities by POMs and metal nodes.

Conjugated Microporous Polymers as Heterogeneous Photocatalysts for Efficient Degradation of a Mustard-Gas Simulant

Compared with traditional metal-based photosensitizers, heterogeneous and organic photocatalysts with visible-light activity are more environmentally friendly and sustainable. The simultaneous introduction of electron-rich and electron-deficient units in donor-acceptor typed conjugated microporous polymer (CMP) photocatalysts can significantly enhance their visible-light harvesting and separation efficiency of photogenerated carriers. Here, two carbazole-based CMPs (CzBSe-CMP and CzBQn-CMP) were successfully constructed through a cost-effective process. They show inherent porosity with large Brunauer-Emmett-Teller surface area and excellent thermal and chemical stability. Their photoelectric properties, energy levels, optical band gaps, transient photocurrent response, and photocatalytic activity could be conveniently tailored through tuning the electron-deficient moiety in polymer networks. More importantly, CzBSe-CMP was found to be a superior solid photocatalyst for selective photo-oxidation of mustard gas simulant 2-chloroethyl ethyl sulfide into a nontoxic product by using molecular oxygen as a sustainable oxygen source under visible-light illumination. In addition, the obtained CMP-based photocatalysts also showed excellent recyclability and could be reutilized through adding more simulants or a simple separation procedure. The current contribution provides great application prospects for CMPs as metal-free, solid photocatalysts in organic transformation and environmental protection.

Versatile catalysts constructed from hybrid polyoxomolybdates for simultaneously detoxifying sulfur mustard and organophosphate simulants

Twelve new hybrid dimers based on carboxylic acid ligand modified polyoxomolybdates were prepared, which can rapidly oxidize the mustard gas simulant, CEES, and hydrolyze the nerve agent simulant, DECP, at room temperature.

Mono-transition-metal-substituted polyoxometalate intercalated layered double hydroxides for the catalytic decontamination of sulfur mustard simulant

The mono-transition-metal-substituted polyoxometalate intercalated layered double hydroxides Zn₂Cr-LDH-PW₁₁M can effectively catalyze the oxidative decontamination of a sulfur mustard simulant.

Introduction to chemical warfare agents, relevant simulants and modern neutralisation methods

This short review presents the current main chemical warfare agents and their most relevant simulants, and the recent catalytic and selective methods for their soft neutralization, potentially usable in the future as an alternative to “heavy” methods for decontamination.

Three new Strandberg-type phenylphosphomolybdate supports for immobilizing horseradish peroxidase and their catalytic oxidation performances

Three new Strandberg-type polyoxometalate TM-(PhP)2Mo5 supports for immobilizing HRP showed high adsorption capacity and good catalytic oxidation activity.