Insights into Catalytic Hydrolysis of Organophosphate Warfare Agents by Metal-Organic Framework NU-1000

Metal organic frameworks (MOFs) have been reported to be versatile catalysts because of their amenability to modular design and tunability. Recently, a series of zirconium-based MOFs have been used to catalyze the hydrolytic destruction of chemical warfare agents (CWAs) that contain phosphate ester bonds. Here, we adopt density functional theory calculations to study the hydrolysis of the CWA simulant methylparaoxon on the Zr-based MOF NU-1000. Our calculated energy barriers are in quantitative agreement with previous experimental kinetics data. Comparison between uncatalyzed aqueous hydrolysis and the MOF-catalyzed reaction reveals the origin of the catalytic effects of NU-1000 and shows a resemblance to enzymatic catalysis of similar reactions. The effect of node distortion on the catalytic mechanism is also examined, and the results are consistent with experimental findings, where the distorted node of NU- 1000 shows an increase in the rate of methylparaoxon hydrolysis compared to the completely hydrated regular form of NU-1000.