Modeling of Diffusion of Acetone in UiO-66

Abstract

Highly porous zirconium-based metal−organic frameworks (MOFs) have been widely studied as materials for sorption and destruction of chemical warfare agents (CWAs). It is important to understand the diffusion of CWAs, their reaction products, and environmental molecules through MOFs to utilize these materials for protection against CWA threats. As a first step toward this goal, we study adsorption and diffusion of acetone in pristine UiO-66. We have chosen to study UiO-66 because it has been demonstrated to be effective for destruction of CWAs and simulants; we use acetone because it is a prototypical polar organic molecule small enough to be expected to diffuse fairly rapidly through nondefective UiO-66. We specifically examine the impact of framework flexibility and hydrogen bonding between acetone and the OH groups on the nodes of the framework on the diffusivity of acetone. We find that inclusion of flexibility is essential for meaningful predictions of diffusion of acetone. We have identified the dynamics of the three linkers making up the triangular window between adjacent pores as the critical factor in controlling diffusion of acetone. We demonstrate from experiments and first-principles calculations that acetone readily hydrogen bonds to UiO-66 framework OH groups. We have modified the classical potential for UiO-66 to accurately model the framework−acetone hydrogen bonds, which are not accounted for in many MOF potentials. We find that hydrogen bonding decreases the diffusivity by about 1 order of magnitude at low loading and about a factor of 3 at high loading. Thus, proper accounting of hydrogen bonding and framework flexibility are both critical for obtaining physically realistic values of diffusivities for acetone and similar-sized polar molecules in UiO-66.

Water Bridges Substitute for Defects in Amine-Functionalized UiO-66, Boosting CO2 Adsorption

“…While the two defect patterns appear identical, the relative position of each linker’s functional group is different, providing each pattern with a unique environment. As was done in earlier studies, exposed oxygens of the metal oxide that were produced during ligand excision were protonated, and the MOFs were modeled as rigid frameworks, as done for other UiO-66 studies. − The Lennard-Jones parameters of zirconium atoms were taken from UFF, while the parameters of the remainder of the atoms were taken from DREIDING . The partial charges of the framework atoms were determined from first principles.…”

Modelling drug adsorption in metal–organic frameworks: the role of solvent

“…This higher adsorption in experiments can be attributed to the stronger interaction of the carboxylic group with the defect sites on the zirconium nodes of the UiO-AZB in our experiments. 51,52 Similarly, the adsorption of 5-FU and HU in the exterior pores was 8.59 and 72.86 molecules accounting for 121.92 mg g −1 and 605.41 mg g −1 . Thus, the adsorption of 5-FU and HU is within 2% and 110% to that of experimentally measured adsorption, respectively.…”

Manipulating Active Sites of 2D Metal–Organic Framework Nanosheets with Fluorescent Materials for Enhanced Colorimetric and Fluorescent Ammonia Sensing

“…Hydrogen bonding between acetone and OH groups on framework nodes has been reported previously. [34] Exfoliation can be initially observed in TEM image shown in Figure 1b, where smaller agglomerations of nanosheets can be observed. Upon further sonication, contact mode atomic force microscopy (AFM) images of multiple individual nanosheets of Zn-BTC can be obtained.…”