(569i) Diffusion and Adsorption of Polar Molecules in Defective Uio-66

Metal-Organic Frameworks (MOFs) are crystalline porous materials having potential applications in catalysis, gas storage, and membrane separation. The UiO-6x MOF family has shown impressive catalytic and gas adsorption properties and has promising degradation capabilities for Chemical Warfare Agents (CWAs). UiO-66 synthesis produces defects impacting its mechanical and chemical properties, producing labile sites for catalysis. To understand how polar molecules will behave in defective MOFs, we studied the diffusion of IPA in defective UiO-66. We model structures having 25% missing linker defects. We calculated diffusion coefficients for different defective structure patterns to check the impact of defect positions on diffusion with increasing IPA loading per formula unit (f.u.). Two distinct framework charge types were considered to study the effect of framework charges on self-diffusion at different IPA loading per f.u. At low to moderate loading, defective structures have higher self-diffusivity than defect-free structures. However, diffusivity decreases at higher loading. We attribute the decrease in diffusion at high loading to the formation of hydrogen-bonded structures between multiple IPA molecules and defect sites. Defective UiO-66 shows higher adsorption than the pristine structure above saturation pressure at room temperature. Maximum self-diffusivities are observed at different IPA loading per f.u., which are justified by the pore and window geometries. Results from this study will aid in modeling CWA diffusion in defective UiO-66.