Molecular simulations to investigate the guest-induced flexibility of Pu-UiO-66 MOF

Abstract

Actinide metal-organic frameworks are highly popular because of their significant coordination benefits. Due to production and characterisation challenges, An-MOFs are a relatively less explored coordination polymer. In this study, we considered the experimentally synthesised Pu-UiO-66 MOF, which was the first reported plutonium MOF. In most MOF studies, the framework has been maintained rigid, however, in this case, we investigate both rigidand flexible frameworks. To gain a better understanding of the framework's flexibility, flexible Grand Canonical Monte Carlo (GCMC) simulations were conducted and the calculated results were compared with that of rigid frameworks. Molecular Dynamics (MD) simulations were carried out to examine the effects of framework flexibility of Pu-UiO-66 MOF, a force field-built Grand Canonical Monte Carlo (GCMC) on adsorption of guest molecules, and to analyse the self-diffusion coefficients of acidic gases such as CO2, SO2, and NO2 in the framework. The adsorption isotherms and radial distribution functions for both rigid and flexible frameworks in the presence of gas molecules were compared and analysed using GCMC simulation. Similarly, molecular dynamics simulations including guest molecules were carried out. Following that, the GCMC and MD results were compared and analysed to determine the flexibility of the system. Diffusion studies were conducted at various temperatures and the coefficient of self-diffusion of each gas was examined. In addition, structural analyses, such as angle analysis, were carried out to explore the local changes, such as tilting, observed in the organic ligand derivative. It was also shown that the UFF force field is suitable for Pu-UiO-66.