(645i) Modeling of Adsorption and Diffusion of Chemical Agents and Simulants in UiO-66

Capture and destruction of chemical warfare agents (CWAs) is an active and important field of research. The UiO-6x metal-organic framework (MOF) family is especially promising for both adsorption and chemical reaction of CWAs. Defects, particularly missing linker defects, are critical for the performance of UiO-66 for adsorbing and destroying CWAs. The pores of UiO-66 are too small to allow facile diffusion of CWAs and without defects, the zirconium nodes of the MOFs are not reactive, since they are fully coordinated. This work explores adsorption in the defective structures of MOF UiO-66 having various defect patterns, using the grand canonical Monte Carlo method. Widely studied CWA simulant dimethyl methyl phosphonate (DMMP), another simulant dimethyl phosphite (DMP), CWA sarin (GB), and soman (GD) are included in the adsorption calculations. Two different framework charge types are studied to see their effect on adsorption capacity at low and high pressures. Adsorption of simulants is lower in the case of defective MOFs than pristine UiO-66 at lower pressure, and the opposite trend is observed for high-pressure adsorption. In conjunction with the adsorption capacity of MOFs, self diffusivities of CWA and their simulants at zero loading are calculated for hydroxylated pristine UiO-66, using the dynamically corrected Transition State Theory (dcTST) approach. The parameterization of the force field to include the hydrogen bonding between the CWA/simulants and framework atoms impacts the zero loading self-diffusivities of both CWA and their simulants. The pristine MOF serves as a good starting point to study defective structures in the future.