The effective capture and detoxification of chemical warfare agents (CWAs) is a pressing issue in the modern world. Materials are needed for both the destruction of weapon stockpiles and personal protection via coatings or respirators. Attractive catalysts for these applications include metal-organic frameworks (MOFs) due to their high porosity, large surface area, and chemical functionality that can be tailored to adsorb specific target molecules. Recent experiments have shown that Zr(IV)-MOFs, such as NU-1000, can catalytically degrade organophosphate-based nerve agents by hydrolysis of the phosphate ester bond. In this work, we used density functional theory to investigate the detailed hydrolysis reaction mechanism of the nerve agent simulant methyl-paraoxon at the active site metal node of NU-1000. Through transition state structure analysis and comparison to the uncatalyzed aqueous hydrolysis reaction, the origin of the catalytic effects of NU-1000 were determined. The effect of node distortion on the catalytic mechanism was also examined, and the results were consistent with experimental kinetics data that shows improvement in catalytic efficiency following temperature-induced node dehydration and distortion. We also investigated the hydrolysis mechanisms for the nerve agents sarin and soman on the same NU-1000 node. This research helped uncover differences in the degradation pathways between simulants and actual nerve agents, in an attempt to explain the deviation in kinetic rates between the two molecule types observed in experiments. Understanding these behaviors will allow us to establish design principles that can be used to optimize MOF catalysts for the adsorption and decomposition of toxic chemicals.

Exploring catalytic hydrolysis of organophosphorus nerve agents and their simulants by the metal-organic framework NU-1000

255th National Meeting (2018)

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