How Useful Are Common Simulants of Chemical Warfare Agents at Predicting Adsorption Behavior?

Abstract

Nanoporous materials such as metal–organic frameworks (MOFs) have attractive properties for selective capture of chemical warfare agents (CWAs). For obvious reasons, most research on adsorption of CWAs is performed with simulant molecules rather than real agents. This paper examines how effectively common CWA simulants mimic the adsorption properties of sarin and soman. To this end, we perform molecular simulations in the dilute adsorption limit for four simulants [dimethyl methylphosphonate (DMMP), diethyl chlorophosphate (DCP), diisopropyl fluorophosphate, and dimethyl p-nitrophenyl phosphate (DMNP)] and sarin and soman in a set of 2969 MOFs with experimentally known crystal structures. To establish the robustness of the conclusions with respect to the force field used in these simulations, each system was examined with two independent force fields, a “generic” force field and a density functional theory (DFT)-derived force field we established based on extensive dispersion-corrected DFT calculations of adsorption in the well-known MOF UiO-66. Our results show that when judging the performance of adsorbents using the heat of adsorption, DCP and DMMP are the best simulants for the adsorption of sarin, while DMNP is the best simulant for soman. The adsorption properties of DCP or DMMP show a strong correlation with sarin over a range of MOFs, but the correlation between DMNP and soman is considerably weaker. Comparisons of results with both force fields indicate that our main conclusions are robust with respect to the force field used to define adsorbate–MOF interactions.

Screening for Improved Nerve Agent Simulants and Insights into Organophosphate Hydrolysis Reactions from DFT and QSAR Modeling

“…In addition to predicting free energy barriers for uncatalyzed reactions, the molecular descriptors could potentially be used in new QSAR models for other applications. For instance, different response variables such as binding energies could be implemented to make predictions for uptake in porous materials or for sensing and detection.…”

The Role of Molecular Modeling & Simulation in the Discovery and Deployment of Metal-Organic Frameworks for Gas Storage and Separation

“…257 The primary mechanism of nerve agent function is by disrupting nerve signals to the organs in the body, resulting in symptoms such as seizures, cardiac arrest, and potentially death by asphyxiation. 258,259 Acute exposure to nerve agents can lead to long-term cognitive and behavioral deficits. 260 The adsorption capabilities of MOFs can potentially be exploited to capture chemical warfare agents from the air, 261 e.g., as a filter in a gas mask.…”

“…11b. Sholl et al 259 264 In the shortlist of hydrophobic MOFs, the authors ran (more expensive) GCMC simulations of mustard gas and nerve agents sarin and soman at 13.8 Pa and 0.6 Pa, respectively, an estimate of the lethal concentrations. Of eight MOFs predicted to exhibit the largest sarin, soman, and mustard gas uptakes (the three were strongly correlated), they selected Ni 3 (BTP) 2 (CSD refcode: UTEWOG; see Fig.…”

The Role of Molecular Modeling & Simulation in the Discovery and Deployment of Metal-Organic Frameworks for Gas Storage and Separation

“…184 The primary mechanism of nerve agent function is by disrupting nerve signals to the organs in the body, resulting in symptoms such as seizures, cardiac arrest, and potentially death by asphyxiation. 185,186 Acute exposure to nerve agents can lead to long-term cognitive and behavioral deficits. 187 The adsorption ca-pabilities of MOFs can potentially be exploited to capture chemical warfare agents from the air, 188 e.g., as a filter in a gas mask.…”

“…et al186 simulated adsorption of nerve agents [soman, sarin] at dilute conditions in the CoRE MOFs and compared their heats of adsorption to that of four com-…”