Zirconium Hydroxide-coated Nanofiber Mats for Nerve Agent Decontamination

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.

DFT-Spectroscopy Integrated Identification Method on Unknown Terrorist Chemical Mixtures by Incorporating Experimental and Theoretical GC-MS, NMR, IR, and DFT-NMR/IR Data

In the event of a chemical attack, the rapid identification of unknown chemical agents is critical for an effective emergency response and treatment of victims. However, identifying unknown compounds is difficult, particularly when relying on traditional methods such as gas and liquid chromatography-mass spectrometry (GC-MS, LC-MS). In this study, we developed a density functional theory and spectroscopy integrated identification method (D-SIIM) for the possible detection of unknown or unidentified terrorist materials, specifically chemical warfare agents (CWAs). The D-SIIM uses a combination of GC-MS, nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and quantum chemical calculation-based NMR/IR predictions to identify potential CWA candidates based on their chemical signatures. Using D-SIIM, we successfully verified the presence of blister and nerve agent simulants in samples by excluding other compounds (ethyl propyl sulfide and methylphosphonic acid), which were predicted to be candidates with high probability by GC-MS. The findings of this study demonstrate that the D-SIIM can detect substances that are likely present in CWA mixtures and can be used to identify unknown terrorist chemicals.

In-situ detoxification of schedule-I chemical warfare agents utilizing Zr(OH)4@W-ACF functional material for the development of next generation NBC protective gears

Chemical warfare agents (CWAs) have become a pivotal concern for the global community and spurred a wide spectrum of research for the development of new generation protective materials. Herein, a highly effective self-detoxifying filter consisting of in-situ immobilized Zirconium hydroxide [Zr(OH)4] over woven activated carbon fabric [Zr(OH)4@W-ACF] is presented for the removal of CWAs. It was prepared to harness the synergistic effect of high surface area of W-ACF, leads to high dispersion of CWAs and high phosphilicity and reactivity of [Zr(OH)4]. The synthesized materials were characterized by ATR-FTIR, EDX, SEM, TEM, XPS, TGA, and BET surface area analyzer. The kinetics of  in-situ degradation of CWAs over Zr(OH)4@W-ACF were studied and found to be following the first-order reaction kinetics. The rate constant was found to be 0.244 min-1 and 2.31 × 10-2 min-1 for sarin and soman, respectively over Zr(OH)4@W-ACF. The potential practical applicability of this work was established by fabricating Zr(OH)4@W-ACF as reactive adsorbent layer for protective suit, and found to be meeting the specified criteria in terms of air permeability, tearing strength and nerve agent permeation as per TOP-08-2-501A:2013 and IS-17380:2020. The degradation products of CWAs were analyzed with NMR and GC-MS. The combined properties of dual functional textile with reactive material are expected to open up new exciting avenues in the field of CWAs protective clothing and thus find diverse application in defence and environmental sector.

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.

Protective Multifunctional Fibrous Systems Based on Natural Fibers and Metal Oxide Nanoparticles

In recent years, an unprecedented increase in the development of products and technologies to protect the human being has been observed. Now, more than ever, the world population is exposed to several threats, harmful to their well-being and health. Chemical and biological hazardous agents stand out as one of the biggest threats, not only for the military forces, but also for the civilians. Consequently, it's essential to develop personal protective systems that are able to protect their user, not only passively, but actively, being able to detect, adsorb, degrade and decontaminate pesticides, pollutants, microorganisms and most importantly: chemical/biological warfare agents. One recent strategy for the development of active fibrous structures with improved functions and new properties is their functionalization with nanoparticles (NPs), especially metal oxides. Although their known effectiveness in the decomposition of harmful agents, the NPs could also include other functionalities in the same structure using low quantities of material, without adding extra weight, which is of huge importance for a soldier in the battlefield. The use of natural fibers as the substrate is also very interesting, since this material is a much sustainable alternative when compared to synthetic ones, also providing excellent properties.

Daylight-activated fumigant detoxifying nanofibrous membrane based on thiol-ene click chemistry

Daylight-activated detoxifying nanofibrous membranes (LDNMs) are fabricated by grafting benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BD) and biological thiols successively on poly(vinyl alcohol-co-ethylene) (EVOH) nanofibrous membrane. Taking the merits of photoactivity of BD, high-reactivity of biological thiols, and high specific surface area and porosity of the nanofibrous membrane, 1,3-dichloropropene (1,3-D) can be efficiently detoxified on the LDNMs under daylight irradiation via a thiol-ene click reaction. The detoxification function of the LDNMs is "switched on" by light irradiation and continues by following a cascade of chemical attacks of thiyl radicals formed during the photoexcitation process. The resultant LDNMs present rapid detoxification rate (i.e., t1/2 =~30 min) and massive detoxification amount (i.e., ~12 mg/g) against 1,3-D vapor under ambient conditions. More importantly, the LDNMs perform a detoxification tailing effect after moving the light-irradiated membrane to a dark environment, thus ensuring the protective function in the absence of sufficient light sources. The detoxification property of the LDNMs in an outdoor environment with sunlight irradiation shows comparable results to the lab-scale outcomes, enabling them to serve as innovative materials for personal protective equipment in practical applications. The successful fabrication of LDNMs may inspire new insights into the design of protective materials providing aggressive protection.

Tuning the Lewis acidity of metal-organic frameworks for enhanced catalysis

The kinetics of hydrolysis of dimethyl nitrophenyl phosphate (DMNP), a simulant of the nerve agent Soman, was studied and revealed transition metal salts as catalysts. The relative rates of DMNP hydrolysis by zirconium and hafnium chlorides are in accordance with their Lewis acidity. In situ conversion of zirconium chloride to zirconium oxy-hydroxide was identified as the key step. We propose a precursor-MOF activity relationship.

Dual-purpose high-efficiency air filter paper loaded with reactive zirconium hydroxide for the filtration aerosols and degradation of chemical warfare agents

Traditional air filter papers can only filter toxic aerosols without the function of decontamination. If the poison stagnating in the paper is desorbed, it may pose a secondary threat to personnel and make it more difficult to dispose of the scrapped paper. Using an alkali-free glass fiber as the base material and zirconium hydroxide as the decontaminant, a self-decontaminating air filter paper that can degrade HD and VX simultaneously was successfully prepared by an intra-pulp addition method, with high filtration efficiency, low pressure drop and moderate tensile strength. The physicochemical properties were characterized by FE-SEM, EDX, XRD and TGA, and the results indicated that Zr(OH)₄ was dispersed uniformly in the paper and filled in the interstices of the glass fiber. The preparation of the composite material had no impact on the structure of fibers and Zr(OH)₄. The preparation technology of the self-decontaminating air filter paper was optimized. It was found that the paper with a fiber grammage of 50 g m⁻², the adhesive of 2% and a Zr(OH)₄ retention rate of 175.0 wt% could completely degrade HD and VX, whose conversion rate exceeded 99.0%, and had a tensile strength of 0.1193 kN m⁻¹, a filtration efficiency of 99.995%, and a pressure drop of 313.6 Pa. Using GC-MS to detect the decontamination products, it was speculated that HD mainly underwent hydrolysis and elimination reactions, VX mainly underwent hydrolysis and polymerization reactions, and their products were non-toxic or low-toxic. The reaction kinetics of HD and VX on the paper was investigated and the half-lives were 2.6 h and 16.2 min, respectively, which demonstrated an outstanding degradation performance. This work manifested for the first time that the air filter paper can be optimized as an efficient self-decontaminating material, which will open up new possibilities for the design and manufacture of multifunctional protective materials.

Dual-functional air filter paper with addition of Zr(OH)₄ was prepared by an intra-pulp addition method, whose filtration performance is maintained while the decontamination performance is added for HD and VX.

Facile Fabric Detoxification Treatment Method Using Microwave and Polyethyleneimine Against Nerve Gas Agents

Generally, detoxification fabrics are defined as fabrics that remove or inhibit the production of toxic compounds, especially chemical warfare agents such as nerve gas agents. They are usually prepared using a complicated and time-consuming method. This study suggests a facile treatment method for preparing detoxification fabrics against nerve gas agents using polyethyleneimine and microwave curing. The detoxification properties of polyethyleneimine and microwave-treated polypropylene nonwoven fabric were evaluated using diisopropylfluoro-phosphate, which is a nerve agent simulant. The treated polypropylene fabric decontaminated 53.6% of diisopropylfluorophosphate (DFP) in 2 h at 32 °C, and the half-life of DFP on the surface of the treated fabric was 122 min. The result indicates that the treated fabric can act as a basic organocatalyst for the DFP hydrolysis and has a shorter half-life owing to the large number of amine groups. Therefore, the facile treatment method has the potential for use in the preparation of detoxification fabrics.

Detoxification Properties of Guanidinylated Chitosan Against Chemical Warfare Agents and Its Application to Military Protective Clothing

This study investigates the detoxification properties of guanidinylated chitosan against chemical warfare agents and its application to the preparation of military protective clothing. Guanidinylated chitosan was synthesized by chitosan guanidinylation with cyanamide. The detoxification properties of the guanidinylated chitosan were then evaluated using a chemical warfare agent simulant, called diisopropylfluorophosphate (DFP). Cotton fabric was treated with 1 wt.% of guanidinylated chitosan in acetic acid and water solution using the simple and conventional textile treatment method of pad–dry–cure. The detoxification properties of the guanidinylated chitosan-treated cotton fabric were evaluated to investigate the application of guanidinylated chitosan to the preparation of military protective clothing. Subsequently, 71.3% of DFP was hydrolyzed to non-hazardous diisopropylhydrogenphosphate (DHP) in 2 h because of the base organocatalytic activity of 0.02 g guanidinylated chitosan itself. Moreover, 60.1% of DFP was hydrolyzed by the catalytic activity of the guanidinylated chitosan-treated cotton fabric, which contained only 0.0002 g of guanidinylated chitosan. This result shows that the guanidinylated chitosan itself has detoxification properties for hydrolyzing DFP to DHP, and its detoxification properties can be more efficient when applied to cotton fabric because it showed 84.3% of the detoxification properties with only 1 wt.% of guanidinylated chitosan. For the first time, this study shows that guanidinylated chitosan has considerable detoxification properties and can be used as an agent to prepare protective clothing.

Zirconium-Based Metal-Organic Frameworks for the Catalytic Hydrolysis of Organophosphorus Nerve Agents

Organophoshorus nerve agents are among the most toxic chemicals known to humans, and because of their unfortunate recent use despite international bans, there is an urgent need to develop materials that can effectively degrade these nerve agents. Within the past decade, zirconium-based metal-organic frameworks (Zr-MOFs) have emerged as a bioinspired class of materials capable of rapidly hydrolyzing these compounds and significantly diminishing their toxicity. Both experimental and computational insights have guided the design of Zr-MOFs, leading to the development of catalysts capable of detoxifying nerve agents and simulants, chemicals with similar functionality but lower toxicity, via hydrolysis within seconds in basic aqueous solutions. While these systems are acceptable for the elimination of stockpile weapons, translating this catalytic performance to filters incorporating Zr-MOFs that can be used in masks or protective clothing is not trivial. As such, a large area of focus recently has been targeted toward integrating these hydrolysis catalysts into protective clothing and gear while retaining the performance from solution-based catalytic systems. This Forum Article provides an overview of the development of Zr-MOFs for the catalytic hydrolysis of organophosphorus substrates, including design principles and mechanistic insights for both solution-based and textile-coated systems. Finally, we highlight the remaining challenges yet to be addressed and offer perspectives on the future directions for this field.

Dye Clicked Thermoplastic Polyurethane as a Generic Platform toward Chromic-Polymer Applications

Chromic dyes responding against external stimuli are useful in various field of applications especially to colorimetric sensors. However, there have been several limitations in generic application because of its cost, stability and reliability. Here, we introduced highly functionalizable polymeric materials as a supporter covalently modified with controlled amount of chromic dyes. The photochromic organic dye (spiropyran) and highly functional thermoplastic polyurethanes (TPU) have been adopted as a representative example. Conventional polymeric solution processes such as film processing, wet-spinning, electrospinning and ink-writing are readily applicable because dye-TPU maintains its own solubility in various organic solvents. Additionally, since the concentration of dye on TPU are precisely controllable, these dye-TPU solution can be adopted in broad range of specific applications, such as secret coding, smart fabric, and chromic polymeric film layer.

Disordered Mesoporous Zirconium (Hydr)oxides for Decomposition of Dimethyl Chlorophosphate

A facile method for the formation of mesoporosity within nonporous zirconium hydr(oxides) (ZrO₂/Zr(OH)₄) is presented and their detoxifying capabilities against dimethyl chlorophosphate (DMCP) are investigated. Nanoaggregates of ZrO₂/Zr(OH)₄ appear to be deposited on larger thin flakes of the same material. H₂O₂ is used to induce surface oxygen vacancies of synthesized ZrO₂/Zr(OH)₄ and, as a consequence, mesopores with an average diameter of 3.1 nm were formed. A surface area of H₂O₂-treated ZrO₂/Zr(OH)₄ was increased by an order of magnitude and shows enhanced reactivity toward DMCP. DRIFTS spectroscopy is employed to assess the reactivity differences between the H₂O₂-treated and untreated ZrO₂/Zr(OH)₄. Peaks at 1175 and 1144 cm^-1 indicate the presence of asymmetric stretching of the O-P-O moiety within dimethyl phosphonate (DMHP), a decomposition product from DMCP, and a zirconium-bound methoxy group, respectively. It is suggested that the decomposition of DMCP proceeds through the consumption of bridged hydroxyl groups (b-OH) for both the untreated and H₂O₂-treated samples, as well as an additional hydrolytic decomposition pathway for the H₂O₂-treated sample.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Fast and Sustained Degradation of Chemical Warfare Agent Simulants Using Flexible Self-Supported Metal-Organic Framework Filters

Self-detoxification filters against lethal chemical warfare agents (CWAs) are highly desirable for the protection of human beings and the environment. In this report, flexible self-supported filters of a series of Zr(IV)-based metal-organic frameworks (MOFs) including UiO-66, UiO-67, and UiO-66-NH₂ were successfully prepared and exhibited fast and sustained degradation of CWA simulants. A half-life as short as 2.4 min was obtained for the catalytic hydrolysis of dimethyl 4-nitrophenyl phosphate, and the percent conversion remained above 90% over a long-term exposure of 120 min, well exceeding those of the previously reported composite MOF filters and the corresponding MOF powders. The outstanding detoxification performance of the self-supported fibrous filter comes from the exceptionally high surface area, excellent pore accessibility, and hierarchical structure from the nano- to macroscale. This work demonstrates, for the first time, MOF-only filters as efficient self-detoxification media, which will offer new opportunities for the design and fabrication of functional materials for toxic chemical protection.

Effect of surface acidity of cyano-bridged polynuclear metal complexes on the catalytic activity for the hydrolysis of organophosphates

Heterogeneous catalysis of cyano-bridged polynuclear metal complexes was examined for the hydrolysis of toxic organophosphates. The surface acidity of cyano-bridged polynuclear metal complexes strongly effects on the catalytic activity.

Chemical Warfare Agents Detoxification Properties of Zirconium Metal-Organic Frameworks by Synergistic Incorporation of Nucleophilic and Basic Sites

The development of protective self-detoxifying materials is an important societal challenge to counteract risk of attacks employing highly toxic chemical warfare agents (CWAs). In this work, we have developed bifunctional zirconium metal-organic frameworks (MOFs) incorporating variable amounts of nucleophilic amino residues by means of formation of the mixed ligand [Zr₆O₄(OH)₄(bdc)_6(1-x)(bdc-NH₂)_6x] (UiO-66-xNH₂) and [Zr₆O₄(OH)₄(bpdc)_6(1-x)(bpdc-(NH₂)₂)_6x] (UiO-67-x(NH₂)₂) systems where bdc = benzene-1,4-dicarboxylate; bdc-NH₂= benzene-2-amino-1,4-dicarboxylate; bpdc = 4,4'-biphenyldicarboxylate; bpdc-(NH₂)₂ = 2,2'-diamino-4,4'-biphenyldicarboxylate and x = 0, 0.25, 0.5, 0.75, 1. In a second step, the UiO-66-xNH₂ and UiO-67-x(NH₂)₂ systems have been postsynthetically modified by introduction of highly basic lithium tert-butoxide (LiO^tBu) on the oxohydroxometallic clusters of the mixed ligand MOFs to yield UiO-66-xNH₂@LiO^tBu and UiO-67-x(NH₂)₂@LiO^tBu materials. The results show that the combination of pre and postsynthetic modifications on these MOF series gives rise to fine-tuning of the catalytic activity toward the hydrolytic degradation of both simulants and real CWAs in unbuffered aqueous solutions. Indeed, UiO-66-0.25NH₂@LiO^tBu is able to hydrolyze both CWAs simulants (diisopropylfluorophosphate (DIFP), 2-chloroethylethylsulfide (CEES), and real CWAs (soman (GD), sulfur mustard (HD)) quickly in aqueous solution. These results are related to a suitable combination of robustness, nucleophilicity, basicity, and accessibility to the porous framework.