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Multifunctional composites that couple high-capacity adsorbents with catalytic nanoparticles (NPs) offer a promising route toward the degradation of organophosphorus pollutants or chemical warfare ...

Bis(2-chloroethyl) sulfide or sulfur mustard (HD) is one of the highest-tonnage chemical warfare agents and one that is highly persistent in the environment. For decontamination, selective oxidation of HD to the substantially less toxic sulfoxide is crucial. We report here a solvent-free, solid, robust catalyst comprising hydrophobic salts of tribromide and nitrate, copper(II) nitrate hydrate, and a solid acid (NafionTM) for selective sulfoxidation using only ambient air at room temperature. This system rapidly removes HD as a neat liquid or a vapor. The mechanisms of these aerobic decontamination reactions are complex, and studies confirm reversible formation of a key intermediate, the bromosulfonium ion, and the role of Cu(II). The latter increases the rate four-fold by increasing the equilibrium concentration of bromosulfonium during turnover. Cu(II) also provides a colorimetric detection capability. Without HD, the solid is green, and with HD, it is brown. Bromine K-edge XANES and EXAFS studies confirm regeneration of tribromide under catalytic conditions. Diffuse reflectance infrared Fourier transform spectroscopy shows absorption of HD vapor and selective conversion to the desired sulfoxide, HDO, at the gas–solid interface. Decontamination of sulfur-containing chemical warfare agents can be achieved through selective, air-based oxidation. Here a solid, solvent-free catalyst for aerobic oxidative decontamination of sulfur mustard is reported.

Understanding mechanisms of decontamination of chemical warfare agents (CWA) is an area of intense research aimed at developing new filtration materials to protect soldiers and civilians in case of state-sponsored or terrorist attack. In this study, we employed complementary structural, chemical, and dynamic probes and in situ data collection, to elucidate the complex chemistry, capture, and decomposition of the CWA simulant, dimethyl chlorophosphonate (DMCP). Our work reveals key details of the reactive adsorption of DMCP and demonstrates the versatility of zeolitic imidazolate framework (ZIF-8) as a plausible material for CWA capture and decomposition. The in situ synchrotron-based powder X-ray diffraction (PXRD) and pair distribution function (PDF) studies, combined with Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), zinc K-edge X-ray absorption near edge structure (XANES), and Raman spectroscopies, showed that the unique structure, chemical state, and topology of ZIF-8 enable accessibility, adsorption, and hydrolysis of DMCP into the pores and revealed the importance of linker chemistry and Zn2+ sites for nerve agent decomposition. DMCP decontamination and decomposition product(s) formation were observed by thermogravimetric analysis, FT-IR spectroscopy, and phosphorus (P) K-edge XANES studies. Differential PDF analysis indicated that the average structure of ZIF-8 (at the 30 A scale) remains unchanged after DMCP dosing and provided information on the dynamics of interactions of DMCP with the ZIF-8 framework. Using in situ PXRD and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), we showed that nearly 90% regeneration of the ZIF-8 structure and complete liberation of DMCP and decomposition products occur upon heating.

We report an all solid dry complex oxidizing agent against sulfur mustard (HD) and its simulant 2-Chloroethyl ethyl sulfide (2-CEES). Polymer complexes of poly(N-vinylpyrrolidone) (PVP) with hydrog...

Mesoporous copper–titanium dioxide (Cu/TiO2) composite aerogels with

Developing novel and more efficient filters for chemical warfare agent (CWA) decomposition remains an important challenge for modern technology due to the continuous threat those weapons present in...

Operando conditions, such as the presence of H2O, can dramatically alter the reaction pathways of molecular interactions on a surface. Here, we determine how water affects the decomposition chemistry of SO2(g) on dry and wet Zr(OH)4 powder, a material being transitioned for battlefield chemical sequestration and decomposition. Diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy reveal that SO2 decomposition products on dry and wet Zr(OH)4 differ significantly. Sulfites (sulfates) dominate on dry (wet) Zr(OH)4 surfaces. Kinetic analysis of the wet surface shows that H2O interacts with SO2 initially and then with surface OH sites, indicating that the mechanism to form sulfates requires water molecules. The combined IR spectra and density functional theory calculations confirm that sulfites and sulfates bind to both surface terminal and bridging OH sites.

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 ...

We report computational studies of (O,O-dimethyl)-(O-4-nitrophenyl)-phosphate (DMNP) and (O,O-dimethyl)-(O-phenyl)-phosphate (DMPP) decomposition by the Zr-substituted Polyoxometalate {α-PW11O39Zr(μ-OH)(H2O)}4−, which has been recently shown to be a catalytic active species in the reaction of (Et2NH2)8[{α-PW11O39Zr(μ-OH)(H2O)}2]·7H2O with nerve agents. We studied two possible mechanisms of this reaction described as “hydrolysis first” and “OH-transfer first”. Both reaction pathways are initiated from the same pre-reaction complex (H2O)-(OH)-POM-(nerve agent). The “hydrolysis first” pathway starts by the concerted dissociation of the adsorbed water molecule and nucleophilic addition of the resulting OH group to the nerve agent. Conversely, the “OH-transfer first” pathway starts by nucleophilic addition of the Zr-coordinated OH ligand to the phosphorus of the nerve agent simulant. Calculations show that the “OH-transfer first” pathway exhibits a lower energy barrier for the decomposition of DMPP by ZrPOM. Thus, the presence of a hydroxo ligand in the coordination sphere of Zr(IV) introduces a mechanism switch from “hydrolysis first” [which was recently reported for the Sarin (GB) decomposition mechanism by the hexaniobate POM Cs8Nb6O19] to “OH-transfer first”. These findings imply that the pH of the catalytic solution could play a critical role and potentially control the mechanism of nerve agent and simulant decomposition by polyoxometalates. We also predict and corroborate that the presence of a strong electron-withdrawing para-substituent in the substrate phenyl group accelerates this reaction: DMNP decomposition by ZrPOM occurs with a smaller rate-limiting energy barrier. The calculations reveal several factors of the DMNP decomposition by the Zr(IV)-substituted polyoxometalates that provide design elements of Zr-based materials (including MOFs and POMs) for catalytic CWA decomposition under ambient conditions.

Multifunctional composites that couple high-capacity adsorbents with catalytic nanoparticles (NPs) offer a promising route toward the degradation of organophosphorus pollutants or chemical warfare agents (CWAs). We couple mesoporous TiO

Zr-based metal organic frameworks (MOFs) have been recently shown to be among the fastest catalysts of nerve-agent hydrolysis in solution. We report a detailed study of the adsorption and decomposition of a nerve-agent simulant, dimethyl methylphosphonate (DMMP), on UiO-66, UiO-67, MOF-808, and NU-1000 using synchrotron-based X-ray powder diffraction, X-ray absorption, and infrared spectroscopy, which reveals key aspects of the reaction mechanism. The diffraction measurements indicate that all four MOFs adsorb DMMP (introduced at atmospheric pressures through a flow of helium or air) within the pore space. In addition, the combination of X-ray absorption and infrared spectra suggests direct coordination of DMMP to the Zr6 cores of all MOFs, which ultimately leads to decomposition to phosphonate products. These experimental probes into the mechanism of adsorption and decomposition of chemical warfare agent simulants on Zr-based MOFs open new opportunities in rational design of new and superior decontaminat...

A strategy is developed to enhance the barrier protection of polyethylene oxide (PEO)-metal-organic framework (MOF) composite films against chemical warfare agent simulants. To achieve enhanced protection, an impermeable high-aspect-ratio filler in the form of Laponite RD (LRD) clay platelets was incorporated into a composite PEO film containing MOF UiO-66-NH2. The inclusion of the platelets aids in mitigating permeation of inert hydrocarbons (octane) and toxic chemicals (2-chloroethyl ethyl sulfide, 2-CEES) of dimensions/chemistry similar to prominent vesicant threats while still maintaining high water vapor transport rates (WVTR). By utilizing small-angle neutron scattering, small-angle X-ray scattering, and wide-angle X-ray scattering, the LRD platelet alignment of the films was determined, and the structure of the films was correlated with performance as a barrier material. Performance of the membranes against toxic chemical threats was assessed using permeation testing of octane and 2-CEES, a common simulant for the vesicant mustard gas, and breathability of the membranes was assessed using WVTR measurements. To assess their robustness, chemical exposure (in situ diffuse reflectance infrared Fourier transform spectroscopy) and mechanical (tensile strength) measurements were also performed. It was demonstrated that the barrier performance of the film upon inclusion of the LRD platelets exceeds that of other MOF-polymer composites found in the literature and that this approach establishes a new path for improving permselective materials for chemical protection applications.

A wide range of chemical warfare agents and their simulants are catalytically decontaminated by a new one-dimensional polymeric polyniobate (P-PONb), K12 [Ti2 O2 ][GeNb12 O40 ]⋅19 H2 O (KGeNb) under mild conditions and in the dark. Uniquely, KGeNb facilitates hydrolysis of nerve agents Sarin (GB) and Soman (GD) (and their less reactive simulants, dimethyl methylphosphonate (DMMP)) as well as mustard (HD) in both liquid and gas phases at ambient temperature and in the absence of neutralizing bases or illumination. Three lines of evidence establish that KGeNb removes DMMP, and thus likely GB/GD, by general base catalysis: a) the k(H2 O)/k(D2 O) solvent isotope effect is 1.4; b) the rate law (hydrolysis at the same pH depends on the amount of P-PONb present); and c) hydroxide is far less active against the above simulants at the same pH than the P-PONbs themselves, a critical control experiment.

Electrical impedance spectroscopy, in conjunction with the metal–organic framework (MOF) UiO-66-NH2, is used to detect trace levels of the explosive simulant 2,6-dinitrotoluene. The combination of porosity and functionality of the MOF provides an effective dielectric structure, resulting in changes of impedance magnitude and phase angle. The promising data indicate that MOFs may be used in low-cost, robust explosive detection devices.

A wide range of chemical warfare agents and their simulants are catalytically decontaminated by a new one-dimensional polymeric polyniobate (P-PONb), K12[Ti2O2][GeNb12O40]⋅19 H2O (KGeNb) under mild conditions and in the dark. Uniquely, KGeNb facilitates hydrolysis of nerve agents Sarin (GB) and Soman (GD) (and their less reactive simulants, dimethyl methylphosphonate (DMMP)) as well as mustard (HD) in both liquid and gas phases at ambient temperature and in the absence of neutralizing bases or illumination. Three lines of evidence establish that KGeNb removes DMMP, and thus likely GB/GD, by general base catalysis: a) the k(H2O)/k(D2O) solvent isotope effect is 1.4; b) the rate law (hydrolysis at the same pH depends on the amount of P-PONb present); and c) hydroxide is far less active against the above simulants at the same pH than the P-PONbs themselves, a critical control experiment.

Matrix isolation infrared spectroscopy has been combined with theoretical calculations for the characterization of the 1:1 hydrogen-bonded complex between H 2 O and dimethyl methylphosphonate (DMMP). The symmetric O-H stretching mode was observed to shift 203 cm - 1 to lower energy upon hydrogen bond formation, while a 32 cm - 1 blue shift was noted for the H-O-H bending mode of the H 2 O subunit in the complex. These values compare extremely well with the (unscaled) shifts of -203 and +32 cm - 1 , respectively, that were calculated theoretically at the MP2/6-31+G** level. Additional perturbed modes of the DMMP subunit were observed, shifted relative to the parent band position. The greatest perturbation was to the P=O stretching mode near 1270 cm - 1 , where a shift of -17 cm - 1 was observed (-21 cm - 1 calculated theoretically). This suggests that the site of hydrogen bonding in the complex is at the P=O group, in agreement with theoretical calculations. The binding energy ΔE° for the 1:1 complex was calculated to be -7.7 kcal/mol.

Adsorption equilibria and NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework (MOF) HKUST-1, or Cu(3)(BTC)(2) (BTC = 1,3,5-benzenetricarboxylate). Ammonia capacities determined from chemical breakthrough measurements show significantly higher uptake capacities than from adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu(3)(BTC)(2) framework. Indeed, (1)H MAS NMR reveals that a major disruption of the relatively simple spectrum of Cu(3)(BTC)(2) occurs to generate a composite spectrum consistent with Cu(OH)(2) and (NH(4))(3)BTC species under humid conditions-the anticipated products of a copper(II) carboxylate reacted with limited ammonia. These species are not detected under dry conditions; however, reaction stoichiometry combined with XRD results suggests the partial formation of an indeterminate diammine copper (II) complex with some residual Cu(3)(BTC)(2) structure retained. Cu(II)-induced paramagnetic shifts exhibited by various species in (1)H and (13)C MAS NMR spectra are consistent with model compounds and previous literature. Although results show extensive ammonia capacity of Cu(3)(BTC)(2), much of the capacity is due to reaction with the structure itself, causing a permanent loss in porosity and structural integrity.

Current technology-based efforts are focusing on a nanotechnology approach to sorbent development for air purification applications. Metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) are two novel classes of materials that allow for specific functionalities to be designed directly into a porous framework. This report is the second in a series of summary reports based on the evaluation of samples from the University of California, Los Angeles. The samples evaluated in this report are a continuation of a baseline series of materials aimed at collecting design rules for future materials; results from this and the previous report will be used to create a second-generation of reactive MOFs and ZIFs for air purification applications. Testing of the novel materials included nitrogen isotherm data, water, and chloroethane adsorption equilibria, and ammonia, cyanogen chloride and sulfur dioxide breakthrough data.

The vapor pressure of pinacolyl methyl phosphonofluoridate [O-( I ,2,2-trimethylpropyl)-methyl phosphonofluoridate. GD] has been measured between -20 and 50 C, using vapor saturation methodology. The current data are in good agreement with data previously measured.

Acetylcholinesterase (AChE) is an interesting research target not only because of its high enzyme catalytic rate but also because of the wide range of health effects resulting from its inhibition. This paper discusses results of a theoretical study of acetylcholinesterase inhibition using several simulation techniques. In the first technique, a novel method was developed and used for predicting the binding affinity of human AChE (huAChE) inhibitors. Results are also presented for classical molecular dynamics and quantum mechanical simulations. Theoretical proton NMR shift results are obtained and compared to experiment, and the importance of the Glu199 residue is discussed in the context of the model.

Research on mitigation of toxic threats is critical to national defense, but is often hazardous. Toxicity generally arises at the molecular level via reactions between toxins and host biomolecules. This lends itself well to simulations from which one may safely derive the insight required for effective preventative or therapeutic response strategies. Thus, we have applied quantum chemical methods to address toxicity arising from both hostile (i.e., nerve agents) and inadvertent (e.g., toxic industrial chemicals) sources. Neurotoxic reactions involving inhibition of the acetylcholinesterase enzyme have been structurally and energetically characterized with mind to mitigating the process. In a complementary effort, interactions between toxins and various catalytic and filtering media have been reported with an aim of improving chemical protection devices.