Computational Exploration of the Catalytic Degradation of Sarin and Its Simulants by a Titanium Metal–Organic Framework

Abstract

The catalytic degradation of chemical warfare agents (CWAs) into nontoxic products by metal organic frameworks (MOFs) has been exclusively focused on Zr-based materials so far, although Ti-MOFs might be also of interest owing to the well-known capacity of Ti compounds to efficiently hydrolyze CWAs. Here, we report for the first time a computational exploration of several possible hydrolysis mechanisms on the activated Ti site of a recently discovered highly stable Ti-MOF, MIP-177(Ti), in the presence/absence of water, considering sarin and its simulants dimethyl methylphosphonate and diisopropyl phosphorofluoridate. Density functional theory calculations were performed at the periodic level to accurately assess the main states of the degradation reaction (reactants, transition states, and products) and the associated activation energy barriers for each degradation reaction that are further compared to the corresponding data previously reported for Zr-MOFs. MIP-177(Ti) was demonstrated to be a promising candidate for an efficient degradation of sarin and retention of the resulting products with a level of performance as attractive as that of the best Zr-MOFs reported so far. Furthermore, the simulations performed on the two simulants emphasized that diisopropyl phosphorofluoridate better mimics sarin in terms of the transition states and products obtained during the reaction as well as of the activation energy required to achieve their degradation.