Computational\nAnalysis of Sarin, Soman, and Their\nWater Mixtures in NU-1000: Interaction Mechanisms, Distribution Patterns,\nand Pairing Effects

Due to their extraordinary structural stability under\nhumid conditions,\nzirconium-based metal–organic frameworks (Zr-MOFs) have been\nwidely investigated for the hydrolytic degradation of nerve agents.\nThat said, mechanisms of hydrolysis in the solid state and the participation\nof environmental water are not well understood. This work utilizes\ncomputational techniques to evaluate the behavior of water and two\norganophosphorus nerve agents (sarin and soman) in NU-1000, a Zr-MOF\nwith the characteristic attributes for hydrolytic efficiency under\nhumid conditions. Density functional theory (DFT) calculations reveal\nthat soman binds more favorably to NU-1000 active sites than sarin,\nresulting in different preferential locations of each nerve agent\nwithin the framework. The strength of nerve agent binding is also\nfound to vary depending on the site environment, with more favorable\nbinding of both nerve agents occurring in the c-pores of NU-1000 than\nin the mesopores. Molecular dynamics (MD) simulation results further\nillustrate that free water molecules in NU-1000 prioritize interactions\nwith nerve agents. Given the variation in their affinity for active\nsite interactions, the introduction of different nerve agents to the\nframework results in substantial differences in water distribution\nand behavior. The results give insight into potential variances in\nthe functionality of NU-1000 toward the hydrolysis of each nerve agent.\nMore importantly, they emphasize the significance of considering the\nrole of environmental water in hydrolysis and the possibility of diverse\nreaction variables based on the type of nerve agent and the properties\nof the MOF.