Chemical Warfare Agent Degradation Research Articles

Research Progress in the Degradation of Chemical Warfare Agent Simulants Using Metal-Organic Frameworks.

Chemical warfare agents primarily comprise organophosphorus nerve agents, saliva alkaloids, cyanides, and mustard gas. Exposure to these agents can result in severe respiratory effects, including spasms, edema, and increased secretions leading to breathing difficulties and suffocation. Protecting public safety and national security from such threats has become an urgent priority. Porous metal-organic framework (MOF) materials have emerged as promising candidates for the degradation of chemical warfare agents due to their large surface area, tunable pore size distribution, and excellent catalytic performance. Furthermore, combining MOFs with polymers can enhance their elasticity and processability and improve their degradation performance. In this review, we summarize the literature of the past five years on MOF-based composite materials and their effectiveness in degrading chemical warfare agents. Moreover, we discuss key factors influencing their degradation efficiency, such as MOF structure, pore size, and functionalization strategies. Furthermore, we highlight recent developments in the design of MOF-polymer composites, which offer enhanced degradation performance and stability for practical applications in CWA degradation. These composite materials exhibit good performance in degrading chemical warfare agents, playing a crucial role in protecting public safety and maintaining national security. We can expect to see more breakthroughs in the application of metal-organic framework porous materials for degrading chemical warfare agents. It is hoped that these innovative materials will play a positive role in achieving social stability and security.

Green synthesis of MOF-based textile composites for the degradation of a chemical warfare agent simulant.

A green synthesis of UiO-66-NH2 embedded in chitosan and deposited on textiles has been investigated for the degradation of chemical warfare agents. This method requires no heating or use of toxic solvents. The composite synthesized presents an interesting efficiency in detoxifying common simulants of chemical warfare agents, such as DMNP. In parallel, resistance and permeability tests were also realized in order to confirm the suitability of the composites for further applications.

A review on metal-organic frameworks (MOFs) for toxic gases adsorption

The safe and effective adsorption and degradation of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs) are the current research hotspots. Metal-organic frameworks (MOFs) have been widely used in...

Flexible and MOF-808 uniformly assembled polyimide nanofiber membranes with excellent mechanical properties for rapid degradation of chemical warfare agents

Breathable and soft protective clothing with self-disinfection function is crucial for the practical application of protecting the human body from being killed by corrosive agents. Recent wars and terrorist attacks have motivated researchers to focus on efficient digestion materials as chemical warfare agents (CWAs). Zirconium-based metal–organic frameworks (Zr-MOFs) have been proven to efficiently digest CWAs. However, their powder form limits their application in personal protection. Uniformly and firmly anchoring Zr-MOFs onto fiber materials to form flexible protection fabrics remains a challenge. In this study, a polyimide nanofiber composite membrane loaded with MOF-808 with a cross-linked structure is prepared by combining electrospinning, thermal crosslinking, and the in-situ growth of pre-soaked Zr4+ seeds. The composite film shows excellent softness and mechanical properties with mechanical strength exceeds 20 MPa. Meanwhile, the uniform anchoring of the Zr-MOF on the fibers yields a high specific surface area (453 m2/g) of the composite membrane. In addition, the composite membrane can digest the mustard gas simulant, 2-chloroethyl ethyl sulfide, at a digestion efficiency of 90.9%. This simple and efficient solution provides a new method for the development of breathable, flexible, self-sterilizing materials, which are expected to be applied as protective materials against chemical warfare agents, for human body protection, and in other fields.

Advances in Metal-Organic Frameworks for the Removal of Chemical Warfare Agents: Insights into Hydrolysis and Oxidation Reaction Mechanisms.

The destruction of chemical warfare agents (CWAs) is a crucial area of research due to the ongoing evolution of toxic chemicals. Metal-organic frameworks (MOFs), a class of porous crystalline solids, have emerged as promising materials for this purpose. Their remarkable porosity and large surface areas enable superior adsorption, reactivity, and catalytic abilities, making them ideal for capturing and decomposing target species. Moreover, the tunable networks of MOFs allow customization of their chemical functionalities, making them practicable in personal protective equipment and adjustable to dynamic environments. This review paper focuses on experimental and computational studies investigating the removal of CWAs by MOFs, specifically emphasizing the removal of nerve agents (GB, GD, and VX) via hydrolysis and sulfur mustard (HD) via selective photooxidation. Among the different MOFs, zirconium-based MOFs exhibit extraordinary structural stability and reusability, rendering them the most promising materials for the hydrolytic and photooxidative degradation of CWAs. Accordingly, this work primarily concentrates on exploring the intrinsic catalytic reaction mechanisms in Zr-MOFs through first-principles approximations, as well as the design of efficient degradation strategies in the aqueous and solid phases through the establishment of Zr-MOF structure-property relationships. Recent progress in the tuning and functionalization of MOFs is also examined, aiming to enhance practical CWA removal under realistic battlefield conditions. By providing a comprehensive overview of experimental findings and computational insights, this review paper contributes to the advancement of MOF-based strategies for the destruction of CWAs and highlights the potential of these materials to address the challenges associated with chemical warfare.

Degradation of Chemical Warfare Agent Nitrogen Mustard Using Ferrate (VI).

Chemical warfare agents (CWAs) are one of the most toxic compounds. Degradation of CWAs using decontamination agents is one of the few ways to protect human health against the harmful effects of CWAs. A ferrate (VI)-based potential chemical warfare agent decontaminant was studied for the degradation of persistent nitrogen mustard (tris(2-chloroethyl)amine, HN3). By optimizing the reaction conditions, the complete degradation of HN3 was achieved in 4 min. The degradation products contained mostly reduced Fe species, which confirmed the environmental friendliness of the proposed decontamination solution.

Acute toxicity of organoarsenic chemical warfare agents to Danio rerio embryos

During the 20th century, thousands of tons of munitions containing organoarsenic chemical warfare agents (CWAs) were dumped into oceans, seas and inland waters around the world. As a result, organoarsenic CWAs continue to leak from corroding munitions into sediments and their environmental concentrations are expected to peak over the next few decades. There remains, however, a lack of knowledge about their potential toxicity to aquatic vertebrates, such as fish. The aim of this study was to fill in this gap in research, by investigating the acute toxicity of organoarsenic CWAs on fish embryos, using the model species, Danio rerio. To estimate the acute toxicity thresholds of organoarsenic CWAs (Clark I, Adamsite, PDCA), a CWA-related compound (TPA), as well as four organoarsenic CWA degradation products (Clark I[ox], Adamsite[ox], PDCA[ox], TPA[ox]), standardized tests were performed following the OECD no. 236 Fish Embryo Acute Toxicity Test guidelines. Additionally, the detoxification response in D. rerio embryos was investigated by analysing the mRNA expression of five genes encoding antioxidant enzymes (CAT, SOD, GPx, GR and GST). During the 96 h of exposure, organoarsenic CWAs induced lethal effects in D. rerio embryos at very low concentrations (classified as 1st category pollutants according to GHS categorization), and were therefore deemed to be serious environmental hazards. Although TPA and the four CWA degradation products caused no acute toxicity even at their maximum solubility, the transcription of antioxidant-related genes was altered upon exposure to these compounds, indicating the need for further testing for chronic toxicity. Incorporating the results of this study into ecological risk assessments will provide a more accurate prediction of the environmental hazards posed by CWA-related organoarsenicals.

Ultrasonic Decontamination of Chemical Warfare Agents

Abstract Sonochemistry studies the physical and molecular level changes induced by ultrasonic energy on solutions. Sonochemical degradation of the chemical warfare agents (CWA) may occur due to three successive phenomena based on the principles of acoustic cavitation phenomena: nucleation, growth, and implosive collapse of microbubbles. The sonolytic degradation of CWA was quantified by GC-MS technique, considering the variation of some parameters such as frequency of ultrasonic waves, power control, temperature, and addition of nanoparticles as catalysts to the solution.

In situ construction of hierarchical Fe2O3 nanotube arrays for real-time detection and degradation of 2-CEES gas

Real-time detection and degradation of chemical warfare agents have great importance in both human healthcare and environmental protection. Herein, hierarchical Fe2O3 nanotube arrays were constructed by a simple in situ solvothermal method for effective monitoring of 2-chloroethyl ethyl sulfur enigma (2-CEES). The resultant Fe2O3 sensor exhibited ultrahigh response (9.6) and short response time (3.7 s) to 10 ppm 2-CEES at 170 ℃. The sensor also behaved low detection limit (30 ppb), good stability, and high moisture resistance. Notably, Fe2O3 nanotube arrays demonstrated high degradation capacity (95.2%) (100 ppm, 10 min). Such excellent performance of the portable Fe2O3 sensor for 2-CEES comes from the synergistic effect of multiple microstructural features, active sites, and surface-adsorbed oxygen species at operating temperature. The 2-CEES sensing mechanism of Fe2O3 nanotube arrays has been discussed in detail. This work offers guidance for designing high-performance sensing materials to realize efficient detection of chemical warfare agents.

Aramid nanofibers supported metal-organic framework aerogel for protection of chemical warfare agent

Protective fabrics containing Zr-Based Metal-Organic Frameworks (Zr-MOFs) show great potential in the detoxification of chemical warfare agents (CWAs). However, the current studies still face the challenges of complicated fabrication processes, limited MOF loading mass, and insufficient protection. Herein, we developed a lightweight, flexible and mechanical robust aerogel by in situ growth of UiO-66-NH2 onto aramid nanofibers (ANFs) and assembly of UiO-66-NH2 loaded ANFs (UiO-66-NH2@ANFs) into 3D hierarchically porous architecture. The UiO-66-NH2@ANF aerogels feature high MOF loading of 261 %, high surface area of 589.349 m2 g−1, open and interconnected cellular structure, which provide efficient transfer channels and promote catalytic degradation of CWAs. As a result, the UiO-66-NH2@ANF aerogels demonstrate high 2-chloroethyl ethyl thioether (CEES) removal rate at 98.9 % and a short half-life of 8.15 min. Moreover, the aerogels present good mechanical stability (recovery rate of 93.3 % after 100 cycles under 30 % strain), low thermal conductivity (λ of 25.66 mW m−1 K−1), high flame resistance (LOI of 32 %) and good wearing comfortableness, indicating promising potential in multifunctional protection against CWAs.

Decontamination of mustard sulfur and VX by sodium percarbonate complexed with 1-acetylguanidine as a novel activator.

The peroxide-based decontaminants had attracted great attention for degradation of chemical warfare agents (CWAs) because of their high performance, non-corrosive and environmental-friendly merits. Hydrogen peroxide can be activated by some organic activators to enhance the oxidation ability. In this work, a novel formula based on sodium percarbonate (SPC) complexed with 1-acetylguanidine (ACG) was investigated for decontamination of sulfur mustard (HD) and VX as CWAs. In the experimental results, the active species acetyl peroxide imide acid in the formula aqueous solution was detected in situ by Raman and 13C NMR spectroscopy. The optimized conditions of the decontamination formula (SPC/ACG) were suggested that, the molar ratio of active oxygen and activator ([O]/[ACG]) was 1:1 while the pH value of the formula aqueous solution was about 9. To achieve the decontamination percentage over 99%, the molar ratio of active oxygen to CWA ((O)/(CWA)) needed to be at least 3 for HD and 7 for VX. Meanwhile, the degradation products detected by gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and ion chromatography (IC) indicated that the oxidation and elimination reactions should have occurred on HD molecule, while the degradation of VX mainly originate from the nucleophilic substitution and oxidation reactions.

Versatile crosslinking synthesis of an EDTA-modified UiO-66-NH2/cotton fabric composite for simultaneous capture of heavy metals and dyes and efficient degradation of organophosphate

The metal-organic frameworks/cotton fabric composites (MOFs/CFCs) have emerged as a new type of prospective materials for environmental cleanup, due to their convenient recyclability and high removal efficiency towards hazardous pollutants. However, their practical applications are limited by complicated synthetic conditions, insufficient interface bonding and poor adsorption capacity. Herein, for the first time, a robust ethylenediaminetetraacetic acid (EDTA)-functionalized MOFs/CFC is prepared based on UiO-66-NH2 crystals by using EDTA dianhydride as the cross-linking agent, and applied for simultaneous removal of heavy metals and dyes, as well as degradation of chemical warfare agents. The as-prepared EDTA-UiO-66-NH2/CFC shows extraordinary monocomponent adsorption performance with maximum adsorption capacity of 158.7, 126.2, 131.5, 117.4 and 104.5 mg/g for Cd(II), Cu(II), methylene blue, crystal violet and safranin O, respectively. Interestingly, in metal-dyes binary system, the uptake of Cu(II) by EDTA-UiO-66-NH2/CFC increases significantly when co-existing high concentration of dyes. The results indicate that the synergistic and simultaneous removal of both dyes and metal from complex systems can be realized by EDTA-UiO-66-NH2/CFC via multiple mechanisms. The EDTA-UiO-66-NH2/CFC also exhibits an outstanding catalytic performance for degrading dimethyl 4-nitrophenylphosphate. Besides, it can be reused for several times without obvious decrease of its adsorption and catalysis efficiencies. More impressively, the cross-linking reaction approach can not only anchor UiO-66-NH2 crystals firmly onto cotton fabric, but also facilitate in-situ formation of abundant adsorption sties on the adsorbent surface. Therefore, this work offers a simple and versatile synthetic strategy to develop high-performance environmental material for multiple pollutants remediation.

Catalytic degradation of CWAs with MOF-808 and PCN-222: Toward practical application

Chemical warfare agents, such as nerve agents (GD and VX) and blister agents (HD), have strong toxicities to mankind. In recent years, zirconium-based metal-organic frameworks have been found to be attractive materials for chemical warfare agent degradation. Among them, metal-organic framework-808 (MOF-808) and porous coordination network-222 (PCN-222) were the best. However, few papers pay attention to their practical application. In this work, we prepared MOF-808 and PCN-222 using water phase and organic solvothermal methods, respectively. Their performance for the catalytic degradation of chemical warfare agents under practical decontamination conditions was studied. The results showed that MOF-808 displayed a high potency for catalytic hydrolysis of VX (10,000 mg L−1) in unbuffered solution. PCN-222 exhibited weaker reactivity with a half-life ( t1/2) of 28.8 min. Their different performances might stem from the different connectivity of the Zr6 nodes and framework structures. The results illustrated that the hydrolysis of high-concentration GD required a strong alkaline buffer to neutralize the hydrolysis product of hydrofluoric acid (HF) to avoid catalyst poisoning. When H2O2 was used as the oxidant instead of O2, both zirconium-based metal-organic frameworks performed with effective catalytic potency for HD degradation without any special lighting and so was suitable for practical application, whereas the products obtained from HD, such as HDO2 and V-HDO2, still possessed vesicant toxicity. Overall, MOF-808 prepared via a water-phase synthesis performed with effective catalysis for the degradation of high-concentration VX, GD, and HD with t1/2 of < 0.5, 3.1 and 2.2 min, respectively, exhibiting its potential for practical applications.

Two silver–containing polyoxometalate–based inorganic–organic hybrids as heterogeneous bifunctional catalysts for construction of C–C bonds and decontamination of sulfur mustard simulant

The construction of C–C bonds and degradation of chemical warfare agents (CWAs) are two central organic conversions for future sustainable development. Herein, two remarkable silver-containing polyoxomolybdates-based hybrids (Ag-POMos), [Ag(L)(H2O)2]2[HPMo12O40] (1) and [Ag2(L)2]2[HPMo10V2O40]·4DMSO (2) (L ​= ​4,6-bis(2-pyridyl)-2-aminopyrimidine) were designed and prepared by using silver cation, polyoxomolybdates and multiple N-donors ligand (L). The structure of compound 1 is constructed from an independent Ag center and a keggin-type POMs; compound 2 is composed of two independent Ag centers and a keggin-type POMs, which displays intriguing POM-incorporated 1-D chain structure with hydrogen bonding. Additionally, Ag-POMos catalysts can be severed as the efficient bifunctional catalysts for the three-component Mannich reaction to achieve the construction of C–C bonds and decontamination of sulfur mustard 2-chloroethyl ethyl sulfide (CEES). As bifunctional heterogeneous catalyst, particularly compound 2, exhibits satisfying catalytic performances in the Mannich reaction (conv. 99%; sele. 99%) and the oxidation of CEES (conv. 96%; sele. 96%). Notedly, after three runs, compound 2 maintains excellent catalytic properties, demonstrating its remarkable cycling stability.

Pretreatment method for BX24 Decon water of HD, VX and GD before GC analysis

Chlorine-based decontaminant BX24 is effective for the decontamination of chemical warfare agents (CWAs) VX, GD and HD. In this paper, main factors affecting the agent recovery from decontamination water (decon water) were studied, a pretreatment method was subsequently developed for GC analysis of residual chemical warfare agents in BX24 decon water. Results showed that dichloromethane was the most suitable extractant, especially for sample of VX and GD. Neutralization process should be done to obtain a high recovery, especially for samples under low CWAs concentration and samples with high speed of CWAs degradation like HD decon water. When optimized neutralizer of sodium sulfite or sodium thiosulfate and extractant of dichloromethane were used, where neutralization and extraction were done simultaneously, a recovery above 85% could be obtained for BX24 decon water. The appropriate CWAs concentration ranged from 20 mg/l to 10000 mg/l.

Efficient Decontamination of HD by an Electrophilic Iodine/Carboxylate Composite as an Active Sorbent.

The development of new and efficient decontamination methods has become more relevant in recent years, especially with regard to solid-based decontamination and detoxification systems. The majority of powders used today are dealing with the physical adsorption of chemical warfare agents (CWAs) and their removal from sites without actively destroying them. In this work, we have designed and developed an active solid composite matrix combining organic carboxylate salts and N-iodosuccinimide (NIS) for HD decontamination via oxidation. All the reactions and mechanistic studies for the sorption and degradation of CWAs were conducted using direct polarization and cross polarization solid-state magic-angle spinning nuclear magnetic resonance techniques. Performance toward the sorption and detoxification of HD was tested, exhibiting oxidation within minutes in a mild and selective manner to the nontoxic sulfoxide derivative followed by visible formation of iodine. The results indicate that carboxylate moieties in the matrix are important for stabilizing the positively charged sulfonium ion intermediate and for supplying oxygen for hydrolysis in a water-deficient environment. The NaOBz/NIS composite was shown to be the most efficient in sorbing and converting the water-insoluble agent HD to its nontoxic, water-soluble sulfoxide, which could then be removed from the site with mere water, resulting in less environmental damage and quick remediation.

Washable and Reusable Zr-Metal–Organic Framework Nanostructure/Polyacrylonitrile Fibrous Mats for Catalytic Degradation of Real Chemical Warfare Agents

The use of metal–organic frameworks (MOFs) for an efficient degradation of chemical warfare agents (CWAs) has been an active field of research over the last decade and has attracted an immense interest due to their unique properties. In particular, Zr-MOFs are known to be active for capturing CWAs and even catalyzing their hydrolysis. Here, we devised oleic acid (OA) surface-modified 140 nm sized UiO-66_NH2 nanoparticles (OA-UiO-66_NH2 NPs) with an improved dispersion in solution as compared to the conventional UiO-66_NH2 NPs. We further explored the catalytic degradation performances of OA-UiO-66_NH2 NPs for both real nerve (GD and VX) and blister (HD) agents. The hydrolysis rate was found to be more than three times faster for HD than without catalysts, and the hydrolysis conversion of GD and VX is possible up to 98 and 96.2% for 3 h, respectively. These experimental findings were completed by density functional theory calculations, which elucidated the degradation mechanism for the first time and evaluated their associated energy barriers. OA-UiO-66_NH2 NPs were demonstrated to exhibit a multi-degradation activity of both nerve agents and vesicants comparable to that of UiO-66_NH2 NPs despite the surface modification. Decisively, we successfully prepared fibrous mats by integrating a large amount of OA-UiO-66_NH2 NPs (71 wt %) into the polyacrylonitrile (PAN) polymer by electrospinning. The corresponding composite was shown to exhibit high dispersion of the MOF NPs into the polymer matrix, resulting in fine and uniform thickness of fibers. Remarkably, these fibrous mats revealed excellent reusability and stability for VX decomposition after washing five times with water. We further unraveled that OA-UiO-66_NH2/PAN fibrous mats can be processed on a large scale of utmost importance for future commercialization. These fibrous mats can be envisaged as detoxification membranes and protection clothes and incorporated into toxic gas filter masks for both military/civilian protective applications.

Superelastic and Photothermal RGO/Zr-Doped TiO2 Nanofibrous Aerogels Enable the Rapid Decomposition of Chemical Warfare Agents.

To date, the reckless use of deadly chemical warfare agents (CWAs) has posed serious risks to humanity, property, and ecological environment. Therefore, necessary materials able to rapidly adsorb and securely decompose these hazardous toxics are in urgent demand. Herein, three-dimensional (3D) reduced graphene oxide/Zr-doped TiO2 nanofibrous aerogels (RGO/ZT NAs) are synthesized by feasibly combining sol-gel electrospinning technology and a unidirectional freeze-drying approach. Benefiting from the synergetic coassembly of flexible ZT nanofibers and pliable RGO nanosheets, the hierarchically entangled fibrous frameworks feature ultralow density, superior elasticity, and robust fatigue resistance over 106 compressive cycles. In particular, the RGO incorporation is attributed to the achieved increased surface area, stronger light absorption, and decreased recombination of charge-carriers for photocatalysis. The highly porous 3D RGO/ZT NAs deliver enhanced photothermal catalytic activity for CWA degradation as well as excellent recyclability and good photostability. This work opens fresh horizons for developing advanced 3D aerogel-based photocatalysts in a controlled fashion.

Degradation of G-Type Nerve Agent Simulant with Phase-Inverted Spherical Polymeric-MOF Catalysts.

For the neutralization of chemical warfare agents (CWAs), the generation of an effective catalyst that can be handled safely and applied in personal protective equipment is required. Recently, zirconium-based metal-organic frameworks (Zr-MOFs: UiO-66 and UiO-67) have shown great promise in the degradation of CWAs, including nerve agents. Their catalytic activity is owed to the interplay of both Zr(IV) Lewis acids and Lewis basic groups in the MOF structure. The latter act as proximal bases that can interact with CWAs and improve the catalytic activity of Zr-MOFs. The powder form of MOFs, though, makes them impractical catalysts, as it is challenging to handle, regenerate, and reuse them. To address this challenge, we have synthesized three Zr-MOFs with Lewis basic amino and pyridine functionalities and shaped them in spherical polymeric beads using the phase inversion method. Using this method, we can generate beads with many polymer and MOF combinations (MOF@polymer). We controlled the MOF loading in these beads, and scanning electron microscopy images revealed that the MOF crystals are evenly distributed in the polymeric matrix, ensuring effective catalytic activity. We used these beads to degrade dimethyl p-nitrophenyl phosphate (DMNP), a simulant for the G-type nerve agent. Using 31P NMR, we showed that UiO-66-NH2@PES and UiO-67-(NH2)2@PES PES: poly(ether sulfone) beads destruct DMNP to dimethyl phosphate (DMP) with a half-life (t1/2) of 5.09 and 4.34 min, respectively. Beads made of hydrophobic polymers such as poly(vinylidene fluoride) (PVDF), polystyrene (PS), and Zr-MOFs with pyridine functionalities show that the quantitative hydrolysis of DMNP requires more time compared to that seen with the UiO-66-NH2@PES beads. Our work highlights the facile shaping of MOF powders into beads that can be easily regenerated with their catalytic activity to be maintained for at least three cycles of use.

Degradation of chemical warfare agents by nickel doped titanium dioxide powders: Enhanced surface activity

Here, Nickel doped anatase TiO 2 samples were prepared and characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, specific surface area (BET), porosity determination (BJH) and CO 2 -TPD experiments. DFT calculation was conducted to investigate the oxygen vacancy formation energies and hydroxyl groups activity. The as-prepared Ni 2+ doped TiO 2 samples were used for heterogeneous degradation of chemical warfare agents (CWAs) and a high degradation rate, 92.2% and > 99.5% for sulfur mustard (HD) within 1 h and 12 h, > 99.5% for soman (GD) in less than 30 min, and > 99.5% for VX in less than 5 min was achieved, which were significantly enhanced compared with commercial P25 and anatase TiO 2 nanoparticles under identical conditions. The formation of non-toxic hydrolysis products confirmed the nucleophilic hydrolysis pathway via surface reaction. Integration of experimental and computational methods could well illustrate that surface structure changes of TiO 2 after Ni 2+ doping was the main reason for the superior stoichiometric activity towards CWAs.