Decomposition of the Simulant 2-Chloroethyl Ethyl Sulfide Blister Agent under Ambient Conditions Using Metal-Organic Frameworks

Microwave-assisted hydrothermal synthesis of highly dispersed cerium-zirconium solid solution on Ti3C2Tx nanosheets as an efficient decontamination towards sulfur mustard simulants

The microwave-assisted hydrothermal method has facilitated the straightforward and efficient production of nanoscale CexZr1-xO2/Ti3C2Tx composites. This technique has greatly shortened the synthesis time several hours required by conventional hydrothermal method to merely 10 min. Due to the unique mechanism of microwave-hydrothermal synthesis, composites with excellent crystallinity, uniform particle size, and superior degradation capabilities can be obtained without calcination. Our investigation systematically explores the influence of various factors including mineralizer concentration, dispersant types, synthesis duration, cerium-to-zirconium ratio, as well as MXene content on the material properties. Optimal degradation of 2-chloroethyl ethyl sulfide (2-CEES), sulfur mustard simulants, is achieved using PEG1000 as the dispersant, a cerium-to-zirconium ratio of 1:2, along with 15 mL of MXene, resulting in a remarkably short half-life of only 6.5 min. Furthermore, it is confirmed that the incorporation of cerium atoms into ZrO2 lattice, forming a solid solution that is deposited onto the interlayer and surface of Ti3C2Tx nanosheets, with the composite particles measuring approximately 5.01 nm. The reduced size and increased specific surface area, coupled with the synergistic effects of oxygen vacancies and acid-base sites, ultimately contribute to the hydrolysis and elimination reactions occurring on 2-CEES. This research offers fresh perspectives on the development of novel materials for the degradation of chemical warfare agents.

Interface-regulated S-type core-shell PCN-224@TiO2 heterojunction for visible-light-driven generation of singlet oxygen for selective photooxidation of 2-chloroethyl ethyl sulfide

Selective oxidation of sulfur mustard gas (HD) to non-toxic sulfoxide by the visible-light-catalyzed generation of singlet oxygen (1O2) is a promising degradation strategy. Although PCN-224 can absorb visible light, it suffers from rapid electron-hole recombination and low redox capacity, which limits the performance of HD degradation. Titanium dioxide (TiO2) is an excellent photocatalyst but it lacks visible-light-activity in degrading HD. In this study, PCN-224@TiO2 heterojunction with S-type core-shell structure was synthesized by in-situ growth method to prolong the visible light absorption capacity of TiO2 and inhibit the rapid recombination of PCN-224. The interface formation and internal electric field were optimized by adjusting the Zr/Ti ratio to enhance the charge transfer, redox capacity, electron-hole separation, and visible light absorption. In this study, the formation of heterojunction composites based on Zr-O-Ti linkages is demonstrated by a series of characterization methods. It is demonstrated by experiments and theoretical calculations that PCN-224@TiO2 can generate nearly 100 % 1O2 under visible light conditions without a sacrificial agent, resulting in efficient and selective oxidation of 2-chloroethyl ethyl sulfide (CEES), a simulant of HD, to non-toxic sulfoxide form.

Manganese Oxides with Different Morphologies In Situ Anchored onto Ti3C2Tx Nanosheets: Highly Effective Decontamination toward Sulfur Mustard Simulants

Manganese oxides with porous structure and abundant active sites show potential in degrading sulfur mustard (HD). However, there is an interface effect between the oily liquid HD and nano oxides, and the powder is prone to agglomeration, which leads to incomplete contact and limited degradation ability. Here, we demonstrate a simple hydrothermal method for preparing MnO2/Ti3C2 composites to address this problem. The influence of morphology and crystal structure on performance are examined. Herein, flower-like MnO2 is loaded onto the surface or interlayer of Ti3C2-MXene nanosheets during in situ formation, significantly expanding the specific surface area. It also provides abundant acid-base sites and oxygen vacancies for the degradation of simulants 2-chloro-ethyl-ethyl thioether (2-CEES) without external energy, resulting in a reaction half-life as fast as 12.5 min. The relationship between structure and performance is clearly elaborated through temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS) analyses. Based on in situ attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis, gas chromatography-mass spectrometry (GC-MS) analysis, and density functional theory (DFT) calculation, the proposed degradation pathway of the 2-CEES molecule is a synergistic effect of hydrolysis, elimination, and oxidation. Furthermore, the products are nontoxic or low toxic. Metal oxide/MXene composites are first illustrated for their potential use in degrading sulfur mustard, suggesting new insights into these materials as novel decontamination for decomposing chemical warfare agents.

Robust and highly reactive membranes for continuous disposal of chemical warfare agents: Effects of nanostructure and functionality in MOF and nanochitin aerogel composites

Developing appropriate disposal of stockpiles of chemical warfare agents (CWAs) has gained significant attention as their lethal toxicity seriously harms humanity. In this study, a novel green-fabrication method with UiO-66 catalysts and amine-functionalized chitin nanofibers (ChNFs) was suggested to prepare durable and highly reactive membranes for decomposing chemical warfare agents (CWAs) in the continuous flow system. The strong interaction between ChNFs and the UiO-66 led to stable loading of the UiO-66 on the continuous nano-porous channel of the ChNF reactive membrane even with high loading of UiO-66 (70 wt% of UiO-66 in the ChNF substrate). In addition, the Brønsted base functionalities (-NH2 and -NHCOCH3) of the ChNF enhanced the catalytic activity and recyclability of the UiO-66. The resulting 70-ChNF composites can effectively decompose a nerve agent simulant (methyl paraoxon) even after 7 repeatable cycles, which has been not obtained in the previous UiO-66 catalyst. The ChNF/UiO-66 reactive membranes with 1 m2 of the area decomposed 130 g of CWAs within an hour in a continuous flow system. We believe these robust and highly reactive membranes can provide a sustainable and efficient solution for the massive CWA disposal and also contribute to the advancement of functional membrane material science.

Humidity Enhances the Solid-Phase Catalytic Ability of a Bulk MOF-808 Metal-Organic Gel toward a Chemical Warfare Agent Simulant

Zirconium-based metal-organic frameworks have emerged as promising materials for detoxifying chemical warfare agents (CWAs) due to their remarkable stability and porosity. However, their practical application is hindered by issues with their powder form and poor catalytic performance in solid-phase degradation. To address these challenges, herein, a granular MOF-808 metal-organic gel (G808) is prepared under optimized conditions for catalytic degradation of the simulant 2-chloroethyl ethyl sulfide (2-CEES), a sulfide blister agent, in a neat state under different humidity conditions. The detoxification performance of G808 toward 2-CEES is significantly enhanced as the content of water present increases. The half-life of 2-CEES decontaminated by G808 can be shortened to 816 s, surpassing those of many other benchmark materials. To confirm the mechanism of catalytic degradation, we used gas chromatography, gas chromatography-mass spectrometry, and theoretical calculations. The findings revealed that hydrolysis was the predominant route. Additionally, granular G808 was reusable and adaptable to high-moisture environments, making it an excellent protective material with practical potential.

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.

Feasible Detoxification Coating Material for Chemical Warfare Agents Using Poly(methyl methacrylate)-Branched Poly(ethyleneimine) Copolymer and Metal-Organic Framework Composites

Defense against chemical warfare agents (CWAs) is regarded as a top priority for the protection of humanity, but it still depends on physical protection with severe limitations such as residual toxicity and post-treatment requirement. In this study, a strategically designed functional polymeric substrate was composited with a metal-organic framework catalyst to remove toxicity immediately. A series of PMMA-BPEI copolymers exhibited high processability as a coating and accelerated the catalytic activity of Zr(IV)-based metal-organic framework catalysts (UiO-66). Among them, PMB12_40 composite coating on a cotton fabric, containing a PMMA-BPEI copolymer (PMMA/BPEI = 1/2) and 40% of UiO-66 catalyst, can efficiently decompose nerve agent simulants (methyl-paraoxon) under both liquid phase (t1/2 = 0.14 h) and humidified (t1/2 = 4.8 h) conditions. Moreover, a real agent, GD, was decomposed 100% by PMB12_40 in 4 h at 25 °C and 65% relative humidity. On the basis of superior catalytic activity, the PMB composites are anticipated to be a potential material for active chemical protection coating.

Selective Photodetoxification of a Sulfur Mustard Simulant Using Plasmonic Aluminum Nanoparticles

Plasmonic nanostructures have attracted increasing interest in the fields of photochemistry and photocatalysis for their ability to enhance reactivity and tune reaction selectivity, a benefit of their strong interactions with light and their multiple energy decay mechanisms. Here we introduce the use of earth-abundant plasmonic aluminum nanoparticles as a promising renewable detoxifier of the sulfur mustard simulant 2-chloroethylethylsulfide through gas phase photodecomposition. Analysis of the decomposition products indicates that C-S bond breaking is facilitated under illumination, while C-Cl breaking and HCl elimination are favored under thermocatalytic (dark) conditions. This difference in reaction pathways illuminates the potential of plasmonic nanoparticles to tailor reaction selectivity toward less hazardous products in the detoxification of chemical warfare agents. Moreover, the photocatalytic activity of the Al nanoparticles can be regenerated almost completely after the reaction concludes through a simple surface treatment.

Ultrafast Degradation and High Adsorption Capability of a Sulfur Mustard Simulant under Ambient Conditions Using Granular UiO-66-NH2 Metal-Organic Gels

Zirconium-based metal-organic frameworks (Zr-MOFs) have been considered as prospective materials for the degradation of nerve chemical warfare agents (CWAs) but show poor catalytic performance toward blister agents. Moreover, the powder issues and the poor adsorption capability also remain as the major challenges for the application of Zr-MOFs in practical CWA detoxification. Herein, a series of defected granular UiO-66-NH2 metal-organic gels are synthesized via adjusting the amount of added concentrated hydrochloric acid for the decontamination of 2-chloroethyl ethyl sulfide (2-CEES), a sulfur mustard simulant. The half-life of 2-CEES decontaminated by defected granular UiO-66-NH2 metal-organic gels can be shortened to 7.6 min, which is the highest reported value for MOFs under ambient conditions. The mechanism of decontamination is that the amino group on the linkers in UiO-66-NH2 MOGs undergoes a substitution reaction with 2-CEES to yield 2-(2-(ethylthio)ethylamino)terephthalic acid, which is less toxic and fixed in the frameworks. The recycling test corroborates that the granular UiO-66-NH2 xerogels possess good stability and reusability. Static adsorption and desorption tests show that UiO-66-NH2 xerogels possess a high 2-CEES vapor adsorption capacity of 802 mg/g after exposure for 1 d and only 28 wt % desorption capacity after air exposure for 7 d. The dual function of ultrafast degradation and high adsorption capability provide a firm foundation for using UiO-66-NH2 xerogels as a future protection media.

Robust Nanocellulose/Metal-Organic Framework Aerogel Composites: Superior Performance for Static and Continuous Disposal of Chemical Warfare Agent Simulants

Environment-friendly and robust nanocellulose/metal-organic framework aerogel composites were prepared for effective detoxification of chemical warfare agent simulants both in static and dynamic continuous flow systems. For this, we fabricated a durable porous composite of the UiO-66 catalyst and TEMPO-oxidized cellulose nanofibers (TOCN) to examine as a detoxification filter. Even with over 50 wt % UiO-66, the obtained cellulose aerogel composites exhibited high stability without leaking of UiO-66 for 4 weeks under an aqueous state. The cellulose aerogel composite with 54 wt % UiO-66 showed a quite high surface area (483 m² g^-1) despite the presence of TOCN, which caused fast degradation of methyl paraoxon (MPO), a nerve agent simulant, with a 0.7 min half-life in an aqueous solution with N-ethylmorpholine buffer. This aerogel composite was then examined as the detoxification filter in the continuous flow system under a 7.2 mL h^-1 flow rate, which surprisingly decomposed 53.7 g of MPO within 1 h with 1 m² of the effective area.