Dual-Function Metal-Organic Framework as a Versatile Catalyst for Detoxifying Chemical Warfare Agent Simulants

Defect-enabling zirconium-based metal-organic frameworks for energy and environmental remediation applications

This comprehensive review explores the diverse applications of defective zirconium-based metal-organic frameworks (Zr-MOFs) in energy and environmental remediation. Zr-MOFs have gained significant attention due to their unique properties, and deliberate introduction of defects further enhances their functionality. The review encompasses several areas where defective Zr-MOFs exhibit promise, including environmental remediation, detoxification of chemical warfare agents, photocatalytic energy conversions, and electrochemical applications. Defects play a pivotal role by creating open sites within the framework, facilitating effective adsorption and remediation of pollutants. They also contribute to the catalytic activity of Zr-MOFs, enabling efficient energy conversion processes such as hydrogen production and CO2 reduction. The review underscores the importance of defect manipulation, including control over their distribution and type, to optimize the performance of Zr-MOFs. Through tailored defect engineering and precise selection of functional groups, researchers can enhance the selectivity and efficiency of Zr-MOFs for specific applications. Additionally, pore size manipulation influences the adsorption capacity and transport properties of Zr-MOFs, further expanding their potential in environmental remediation and energy conversion. Defective Zr-MOFs exhibit remarkable stability and synthetic versatility, making them suitable for diverse environmental conditions and allowing for the introduction of missing linkers, cluster defects, or post-synthetic modifications to precisely tailor their properties. Overall, this review highlights the promising prospects of defective Zr-MOFs in addressing energy and environmental challenges, positioning them as versatile tools for sustainable solutions and paving the way for advancements in various sectors toward a cleaner and more sustainable future.

Elucidating the degradation mechanism of the nerve agent A-234 using various detergents: a theoretical investigation

A-234 (ethyl N-[1-(diethylamino)ethylidene]phosphoramidofluoridate) is one of the highly toxic Novichok nerve agents, and its efficient degradation is of significant importance. The possible degradation mechanisms of A-234 by H2O, H2O2, NH3, and their combinations have been extensively investigated by using density functional theory (DFT) calculations. According to the initial intermolecular interaction and the proton transfer patterns between the detergent and the substrate A-234, the A-234 degradation reaction is classified into three categories, denoted as A, B, and C. In modes A and B, the degradation of A-234 by H2O2, H2O, and NH3 is initiated by the nucleophilic attack of the O or N atom of the detergent on the P atom of A-234, coupled with the proton transfer from the detergent to the O or N atom of A-234, whereas in mode C, the direct interaction of H2N-H with the F-P bond of A-234 triggers ammonolysis through a one-step mechanism with the formation of H-F and N-P bonds. Perhydrolysis and hydrolysis of A-234 can be remarkably promoted by introducing the auxiliary NH3, and the timely formed hydrogen bond network among detergent, auxiliary, and substrate molecules is responsible for the enhancement of degradation efficiency.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

Fibrous Zr-MOF Nanozyme Aerogels with Macro-Nanoporous Structure for Enhanced Catalytic Hydrolysis of Organophosphate Toxins

Metal-organic frameworks (MOFs) with Lewis acid catalytic sites, such as zirconium-based MOFs (Zr-MOFs), comprise a growing class of phosphatase-like nanozymes that can degrade toxic organophosphate pesticides and nerve agents. Rationally engineering and shaping MOFs from as-synthesized powders into hierarchically porous monoliths is essential for their use in emerging applications, such as filters for air and water purification and personal protection gear. However, several challenges still limit the production of practical MOF composites, including the need for sophisticated reaction conditions, low MOF catalyst loadings in the resulting composites, and poor accessibility to MOF-based active sites. To overcome these limitations, a rapid synthesis method is developed to introduce Zr-MOF nanozyme coating into cellulose nanofibers, resulting in the formation of processable monolithic aerogel composites with high MOF loadings. These composites contain Zr-MOF nanozymes embedded in the structure, and hierarchical macro-micro porosity enables excellent accessibility to catalytic active sites. This multifaceted rational design strategy, including the selection of a MOF with many catalytic sites, fine-tuning the coating morphology, and the fabrication of a hierarchically structured monolithic aerogel, renders synergistic effects toward the efficient continuous hydrolytic detoxification of organophosphorus-based nerve agent simulants and pesticides from contaminated water.

Starfruit-Shaped Zirconium Metal-Organic Frameworks: From 3D Intermediates to 2D Nanosheet Petals with Enhanced Catalytic Activity

We present the fabrication of a novel Starfruit-shaped metal-organic framework (SMOF) composed of zirconium and Tetra(4-carboxyphenyl)porphine linkers. The SMOF exhibits a unique morphology with edge-sharing two-dimensional (2D) nanosheet petals. Our investigation unravels a captivating transformation process, wherein three-dimensional (3D) shuttle-shaped MOFs form initially and subsequently evolve into 2D nanosheet-based SMOF structures. The distinct morphology of SMOF showcases superior catalytic activity in detoxifying G-type nerve agent and blister agent simulants, surpassing that of its 3D counterparts. This discovery of the 3D-to-2D transition growth pathway unlocks exciting opportunities for exploring novel strategies in advanced MOF nanostructure development, not only for catalysis but also for various other applications.

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.

Sunlight-Driven Photocatalysis for a Set of 3D Metal-Porphyrin Frameworks Based on a Planar Tetracarboxylic Ligand and Lanthanide Ions

Metal-porphyrin frameworks (MPFs) with trivalent lanthanide ions are the most sought-after materials in the past decade. Their porosities are usually complemented by optical properties imparted by the metal nodes, making them attractive multifunctional materials. Here, we report a novel family of 3D MPFs obtained through solvothermal reactions between tetrakis(4-carboxyphenyl) porphyrin (H4TCPP) and different lanthanide sources, yielding an isostructural family of compounds along the lanthanide series: [Ln2(DMF)(TCPP)1.5] for Ln = La, Ce, Nd, Pr, Er, Y, Tb, Dy, Sm, Eu, Gd, and Tm. Photoluminescent properties of selected phases were explored at room temperature. Also, the photocatalytic performance exhibited by these compounds under sunlight exposure is promising for its implementation in organic pollutant degradation. In order to study the photocatalytic activity of Ln-TCPPs in an aqueous medium, methylene blue (MB) was used as a contaminant model. The efficiency for MB degradation was Sm > Y > Yb > Gd > Er > Eu > either no catalyst or no light, obtaining more than 70% degradation at 120 min with Sm-TCPP. These results open the possibility of using these compounds in optical and optoelectronic devices for water remediation and sensing.

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.

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.

Porphyrin-Moiety-Functionalized Metal-Organic Layers Exhibiting Catalytic Capabilities for Detoxifying Nerve Agent and Blister Agent Simulants

The development of very efficient bifunctional catalysts for the simultaneous detoxification of two kinds of the deadliest chemical warfare agents (CWAs), nerve agent and blister agent, is highly desirable. In this study, two porphyrin-based ligands [tetrakis(4-carboxyphenyl) porphyrin (TCPP) and protoporphyrin IX (PPIX)] are introduced into 2D Zr-1,3,5-tris(4-carboxyphenyl)benzene (BTB) metal-organic layers (MOLs), composed of six-connected Zr₆ nodes and the tritopic carboxylate ligand BTB, by a solvent-assisted ligand incorporation method. The loads of TCPP and PPIX are 6.4 and 10.9 wt %, respectively. The detoxification of simulants of the nerve agent and the blister agent was conducted to investigate the catalytic activity of porphyrin-moiety-functionalized MOLs. The reaction half-life of optimal TCPP-functionalized MOL catalyzing the hydrolysis of a nerve agent simulant is only 2.8 min, meanwhile, the half-life of the selective catalytic oxidation of a blister agent simulant is only 1.2 min under LED illumination. More importantly, such a degradation half-life is only about 4 min under natural sunlight (∼60 mW/cm²). To our knowledge, TCPP-functionalized MOL is by far the most efficient catalyst for blister agent simulant degradation under solar light. Therefore, 2D ultrathin MOLs on demand appear to be a promising and efficient material platform for the development of bifunctional catalysts for CWA protection.

Dual-Function Detoxifying Nanofabrics against Nerve Agent and Blistering Agent Simulants

The development of functional materials that can detoxify multiple chemical warfare agents (CWAs) at the same time is of great significance to cope with the uncertainty of CWA use in real-world situations. Although many catalysts capable of detoxifying CWAs have been reported, there is still a lack of effective means to integrate these catalytic-active materials on practical fibers/fabrics to achieve effective protection against coexistence of a variety of CWAs. In this work, by a combination of electrospinning and in situ solvothermal reaction, PAN@Zr(OH)₄@MOF-808 nanofiber membranes were prepared for detoxification of both nerve agent and blistering agent simulants dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (CEES). Under the catalytic effect of the MOF-808 component, DMNP hydrolysis with a half-life as short as 1.19 min was achieved. Meanwhile, an 89.3% CEES removal rate was obtained within 12 h by adsorption and catalysis of MOF-808 and Zr(OH)₄ components at ambient conditions, respectively. PAN@Zr(OH)₄@MOF-808 nanofiber membranes also showed a superior blocking effect on CEES compared to bare PAN and PAN@Zr(OH)₄ nanofiber membranes. Simultaneous protection against DMNP and CEES showed effective inhibition of both simulants for at least 2 h. The preparation method also imparted intrinsically good interfacial adhesion between the components, contributing to the excellent recycling stability of PAN@Zr(OH)₄@MOF-808 nanofiber membranes. Therefore, the prepared composite nanofabrics have great application potential, which provides a new idea for the construction of broad-spectrum protective detoxification materials.

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.

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.

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.

Enhancing the quantum yield of singlet oxygen: photocatalytic degradation of mustard gas simulant 2-chloroethyl ethyl sulfide catalyzed by a hybrid of polyhydroxyl aluminum cations and porphyrin anions

By combining the anionic salt meso-tetra(4-carboxyphenyl)porphyrin (TCPP4-) and the Keggin polyoxometalate cation cluster [Al13O4(OH)24(H2O)12]7+ via a simple ion-exchange method, a hybrid (C48H26N4O8)[Al13O4(OH)24(H2O)12]2(OH)10·18H2O (Al13-TCPP) was prepared and thoroughly characterized as a prototype of polyoxometalate-porphyrin hybrids for the photocatalytic degradation of the mustard gas simulant 2-chloroethyl ethyl sulfide (CEES). The experimental results showed that the catalytic degradation rate of CEES in the presence of Al13-TCPP reached 96.16 and 99.01% in 180 and 90 min in methanol and methanol-water solvent mixture (v/v = 1 : 1), respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and solvent mixture were 39.8 min, -0.017 min-1 and 14.7 min, -0.047 min-1. Mechanism analysis indicated that under visible light irradiation in air, CEES was degraded through a combination of oxidation and alcoholysis/hydrolysis in methanol and the methanol-water solvent mixture. The superoxide radical (O2˙-) and singlet molecular oxygen (1O2) generated by Al13-TCPP selectively oxidized CEES into a non-toxic sulfoxide. The singlet oxygen capture experiments showed that Al13-TCPP (Φ = 0.236) had a higher quantum yield of singlet oxygen generation than H4TCPP (Φ = 0.135) under visible light irradiation in air. The material Al13-TCPP has good reusability, and the degradation rate of CEES can still reach 98.37% after being recycled five times.

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 (t_1/2) 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.

Vapor phase catalytic photooxidation of sulfides to sulfoxides: application to the neutralization of sulfur mustard simulants

A visible-light photocatalytic approach was developped for the aerobic oxidation of sulfides into the corresponding sulfoxides, including sulfur mustard simulants. The heterogeneous catalytic system is selective, operates in the gas...

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.

Detoxification of the Toxic Sulfur Mustard Simulant by a Supramolecular Antidote in Vitro and in Vivo

Although great potential hazards and threats still occur from sulfur mustard, there are no specific medicine or therapy for the intoxication of sulfur mustard. Herein, we have demonstrated a supramolecular approach for the detoxification of the sulfur mustard simulant CEES (4) in vitro and in vivo by carboxylatopillar[5]arene potassium salts (CP[5]AK 1) efficiently based on host-guest interactions. The encapsulation of CEES (4) by the cavity of the pillar[5]arene 2 is driven by C-H···π interactions between CEES (4) and the electron-rich cavity of pillar[5]arene 2, which was investigated by 1H NMR titration, density functional theory studies, and the independent gradient model studies. CEES (4) is degradated to the reactive sulfonium salts quickly in aqueous media, resulting in the alkylation of DNA and proteins. The sulfonium salts can be encapsulated by CP[5]AK 1 efficiently, which accelerates the degradation of the sulfonium salts about 14 times. The cell and animal experiments indicated that the bioactivities of the sulfonium salts are inhibited with the formation of stable host-guest complexes, and CP[5]AK 1 has a good therapeutic effect on the damages caused by CEES (4) at either pre- or post-treatments. Due to the low cytotoxicity and good therapeutic effect, the anionic pillar[5]arenes are expected to be developed as specific antidotes against sulfur mustard (HD).

Green MIP-202(Zr) Catalyst: Degradation and Thermally Robust Biomimetic Sensing of Nerve Agents

Rapid and robust sensing of nerve agent (NA) threats is necessary for real-time field detection to facilitate timely countermeasures. Unlike conventional phosphotriesterases employed for biocatalytic NA detection, this work describes the use of a new, green, thermally stable, and biocompatible zirconium metal-organic framework (Zr-MOF) catalyst, MIP-202(Zr). The biomimetic Zr-MOF-based catalytic NA recognition layer was coupled with a solid-contact fluoride ion-selective electrode (F-ISE) transducer, for potentiometric detection of diisopropylfluorophosphate (DFP), a F-containing G-type NA simulant. Catalytic DFP degradation by MIP-202(Zr) was evaluated and compared to the established UiO-66-NH₂ catalyst. The efficient catalytic DFP degradation with MIP-202(Zr) at near-neutral pH was validated by ³¹P NMR and FT-IR spectroscopy and potentiometric F-ISE and pH-ISE measurements. Activation of MIP-202(Zr) using Soxhlet extraction improved the DFP conversion rate and afforded a 2.64-fold improvement in total percent conversion over UiO-66-NH₂. The exceptional thermal and storage stability of the MIP-202/F-ISE sensor paves the way toward remote/wearable field detection of G-type NAs in real-world environments. Overall, the green, sustainable, highly scalable, and biocompatible nature of MIP-202(Zr) suggests the unexploited scope of such MOF catalysts for on-body sensing applications toward rapid on-site detection and detoxification of NA threats.

Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats

The most recent global health crisis caused by the SARS-CoV-2 outbreak and the alarming use of chemical warfare agents highlight the necessity to produce efficient protective clothing and masks against biohazard and chemical threats. However, the development of a multifunctional protective textile is still behind to supply adequate protection for the public. To tackle this challenge, we designed multifunctional and regenerable N-chlorine based biocidal and detoxifying textiles using a robust zirconium metal-organic framework (MOF), UiO-66-NH₂, as a chlorine carrier which can be easily coated on textile fibers. A chlorine bleaching converted the amine groups located on the MOF linker to active N-chlorine structures. The fibrous composite exhibited rapid biocidal activity against both Gram-negative bacteria (E. coli) and Gram-positive bacteria (S. aureus) with up to a 7 log reduction within 5 min for each strain as well as a 5 log reduction of SARS-CoV-2 within 15 min. Moreover, the active chlorine loaded MOF/fiber composite selectively and rapidly degraded sulfur mustard and its chemical simulant 2-chloroethyl ethyl sulfide (CEES) with half-lives less than 3 minutes. The versatile MOF-based fibrous composite designed here has the potential to serve as protective cloth against both biological and chemical threats.

Photo-assisted enhancement performance for rapid detoxification of chemical warfare agent simulants over versatile ZnIn2S4/UiO-66-NH2 nanocomposite catalysts

Constructing versatile materials with self-detoxification properties are highly desired for emergency destruction of chemical warfare agents (CWAs). Herein, we first reported in-situ fabrication of ZnIn₂S₄/UiO-66-NH₂ nanocomposites (ZnInS/UiO) and their application in catalytic detoxification of two CWA simulants. For nerve agent simulant dimethyl 4-nitrophenyl phosphate (DMNP), the optimal ZnInS/UiO-23.9 displayed 5.9 times increase in hydrolysis rate having the turnover frequency (TOF) of 0.0586 s^-1 under simulated solar light (SSL), which is superior to the reported UiO-based catalysts. Photo-assisted enhancement in DMNP detoxification was due to photothermal effect of ZnInS and close interfacial contact in ZnInS/UiO heterostructures, facilitating instantaneous heat transfer from ZnInS to UiO catalytic sites. As for mustard gas surrogate 2-chloroethyl ethyl sulfide (CEES), under SSL irradiation for 15 min, ZnInS/UiO-23.9 can eliminate 96.7% of CEES in droplet experiment, being 4.17 and 3.24 times of ZnInS and UiO accordingly. It was ascribed to spatial separation of photoinduced electron-hole pairs and photothermally-assisted charge transfer in ZnInS/UiO composites, improving catalytic activity for CEES detoxification. Besides, the detected products suggested that CEES conversion underwent reductive dechlorination, radical reactions and hydrolysis. This study can be extended to other multifunctional catalysts based on metal-organic frameworks and provides new opportunities for photoassisted enhanced detoxification of CWAs.

Reduced polyoxomolybdate immobilized on reduced graphene oxide for rapid catalytic decontamination of a sulfur mustard simulant

Keggin-type polyoxometalates (POMs) were immobilized on poly(diallyldimethylammonium chloride) (PDDA) functionalized reduced graphene oxide (rGO) by a facile and broad-spectrum hydrothermal method. The prepared POMs@PDDA-rGO composites (POM = H3PMo12O40, H3PW12O40, H5PMo10V2O40) have been thoroughly characterized using a series of techniques. The three composites can catalyze the oxidative decontamination of a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES) in the order of PMo12@PDDA-rGO > PMo10V2@PDDA-rGO > PW12@PDDA-rGO. Notably, under ambient conditions PMo12@PDDA-rGO can convert 99% of CEES within 30 min in the presence of nearly stoichiometric aqueous H2O2 (3 wt%) and its catalytic activity is significantly higher than that of homogeneous H3PMo12O40. XPS spectral analysis and control experiments indicate that the Mo center of POM is reduced from +6 to +5 during the hydrothermal process, and the excellent catalytic performance is related to the reduction of Mo. Moreover, the PMo12@PDDA-rGO composite is stable during the decontamination process and it can be used for at least five cycles without loss of activity.

Product Inhibition and the Catalytic Destruction of a Nerve Agent Simulant by Zirconium-Based Metal-Organic Frameworks

Rapid degradation/destruction of chemical warfare agents, especially ones containing a phosphorous-fluorine bond, is of notable interest due to their extreme toxicity and typically rapid rate of human incapacitation. Recent studies of the hydrolytic destruction of a key nerve agent simulant, dimethyl 4-nitrophenylphosphate (DMNP), catalyzed by Zr₆-based metal-organic frameworks (MOFs), have suggested deactivation of the active sites due to inhibition by the products as the reaction progresses. In this study, the interactions of two MOFs, NU-1000 and MOF-808, and two hydrolysis products, dimethyl phosphate (DMP) and ethyl methyl phosphonate (EMP), from the hydrolysis of the simulant (DMNP) and nerve agent ethyl methylphosphonofluoridate (EMPF), resembling the hydrolysis degradation product of the G-series nerve agent, Sarin (GB), have been investigated to deconvolute the effect of product inhibition from other effects on catalytic activity. Kinetic studies via in situ nuclear magnetic resonance spectroscopy indicated substantial product inhibition upon catalyst activity after several tens to several thousand turnovers, depending on specific conditions. Apparent product binding constants were obtained by fitting initial reaction rates at pH 7.0 and pH 10.5 to a Langmuir-Freundlich binding/adsorption model. For the fits, varying amounts/concentrations of candidate inhibitors were introduced before the start of catalytic hydrolysis. The derived binding constants proved suitable for quantitatively describing product inhibition effects upon reaction rates over the extended time course of simulant hydrolysis by aqua-ligand-bearing hexa-zirconium(IV) nodes.

Enzymatic Cascade Reactions Mediated by Highly Efficient Biomimetic Quasi Metal-Organic Frameworks

The integration of chemo- and enzymatic catalysis for effective multistep cascades has presented critical challenges for decades. In this work, the biomimetic quasi NH₂-MIL-101 (qNM) with highly efficient peroxidase-like activity was synthesized via a palmitic acid-induced strategy followed by pyrolysis. The effects of the amount of palmitic acid and calcination temperature on the synthesis of qNM were optimized. It was found that qNM was an excellent catalyst for oxidations of various peroxidase substrates, and a possible mechanism was proposed, i.e., the presence of Fe^II species in qNM was responsible for its excellent activity, which facilitated the transition between Fe^II and Fe^III species to produce more hydroxyl radicals by H₂O₂ decomposition. The qNM served as the potential matrix for enzyme immobilization through a cross-linking method, and kinetic studies revealed that the catalytic efficiency (k_cat/K_m) for the immobilized GOx (23.7 mM^-1 s^-1) is comparable to that of free GOx (26.9 mM^-1 s^-1). The immobilized GOx also showed improved stability against high temperatures and organic solvents compared to free GOx, and analysis of the secondary structure of GOx indicated that the improved stability resulted from enzyme rigidity by the intense covalent linkage with qNM. Furthermore, qNM contributed its biomimetic activity to cooperate with a single enzyme (GOx) or two enzymes (β-Gal and GOx) for the enzymatic cascade reactions. Compared with the mixture of each component in the solution, the combination of the single-enzyme system (GOx) or the two-enzyme system (β-Gal and GOx) in qNM achieved 2.67-fold and 1.83-fold enhancements in the activity of catalytic cascades, respectively. This study provides new insights into the construction of effective and synergistic cascade reactions by integrating biomimetic MOF with natural enzyme, which holds potential for applications in biotechnology and ecofriendly and biomimetic catalysis.

Chemical targets to deactivate biological and chemical toxins using surfaces and fabrics

The most recent global health and economic crisis caused by the SARS-CoV-2 outbreak has shown us that it is vital to be prepared for the next global threat, be it caused by pollutants, chemical toxins or biohazards. Therefore, we need to develop environments in which infectious diseases and dangerous chemicals cannot be spread or misused so easily. Especially, those who put themselves in situations of most exposure - doctors, nurses and those protecting and caring for the safety of others - should be adequately protected. In this Review, we explore how the development of coatings for surfaces and functionalized fabrics can help to accelerate the inactivation of biological and chemical toxins. We start by looking at recent advancements in the use of metal and metal-oxide-based catalysts for the inactivation of pathogenic threats, with a focus on identifying specific chemical bonds that can be targeted. We then discuss the use of metal-organic frameworks on textiles for the capture and degradation of various chemical warfare agents and their simulants, their long-term efficacy and the challenges they face.

Macrocycles in Bioinspired Catalysis: From Molecules to Materials

Macrocyclic compounds have been studied extensively as the host molecules in supramolecular chemistry. Their structural characteristics make macrocycles desirable in the field of molecular recognition, which is the key to high catalytic efficiencies of natural enzymes. Therefore, macrocycles are ideal building blocks for the design of bioinspired catalysts. This mini review highlights recent advances ranging from single-molecule to metal-organic framework materials, exhibiting multilevel macrocycle catalysts with unique catalytic centers and substrate-binding affinities.

Paraoxonase Mimic by a Nanoreactor Aggregate Containing Benzimidazolium Calix and l-Histidine: Demonstration of the Acetylcholine Esterase Activity

An anion-mediated preorganization approach was used to design and synthesize the benzimidazolium-based calix compound R1⋅2 ClO₄ ^- . X-ray crystallography analysis revealed that the hydrogen-bonding interactions between the benzimidazolium cations and N,N-dimethylformamide (DMF) helped R1⋅2 ClO₄ ^- encapsulate DMF molecule(s). A nanoreactor, with R1⋅2 ClO₄ ^- and l-histidine (l-His) as the components, was fabricated by using a neutralization method. The nanoreactor could detoxify paraoxon in 30 min. l-His played a vital role in this process. Paraoxonase is a well-known enzyme used for pesticide degradation. The Ellman's reagent was used to determine the percentage inhibition of the acetylcholinesterase (AChE) activity in the presence of the nanoreactor. The results indicated that the nanoreactor inhibited AChE inhibition.

Bifunctional Europium(III) and Niobium(V)-Containing Saponite Clays for the Simultaneous Optical Detection and Catalytic Oxidative Abatement of Blister Chemical Warfare Agents

For the first time, the co-presence in the saponite structure of luminescent Eu^III and catalytic Nb^V metal sites was exploited for the simultaneous detection and catalytic abatement of sulfur-containing blister chemical warfare agents. Metal centers were introduced in structural positions of the saponite (in the interlayer space or inside the inorganic framework) following two different synthetic methodologies. The functionalized saponites were able to reveal the presence of a sulfur mustard simulant (2-chloroethyl)ethyl sulfide (CEES) after few seconds of contact time and more than 80 % of the substrate was catalytically decomposed after 24 h in the presence of aqueous hydrogen peroxide.

One-flow upscaling neutralization of an organophosphonate-derived pesticide/nerve agent simulant to value-added chemicals in a novel Teflon microreactor platform

Synthesizing value-added products from chemical warfare agents is a concept well beyond the usual notion of simply neutralizing the agents.

A NaX zeolite framework containing magnetic MgFe2O4/CdO nanoparticles: synthesis, characterization and catalytic performance in the decontamination of 2-chloroethyl phenyl sulfide (2-CEPS) as a model of sulfur mustard agent

Magnetic MgFe2O4/CdO nanoparticles were immobilized in a zeolite NaX network and their application for the decontamination of sulfur mustard agent simulant 2-CEPS was evaluated.