Understanding the effects of water on the capture of gaseous elemental mercury in UiO-66 using flexible force fields: A computational study

• The adsorption and separation properties of Hg 0 in UiO-66 at 393 K under varying humidity conditions. • The presence of water significantly enhances the adsorption of Hg 0 at different relative humidity. • The adsorption mechanism were revealed by the structural and dynamical properties. This study investigates the adsorption and separation properties of elemental mercury in UiO-66 at 393 K under varying humidity conditions using the Grand Canonical Ensemble Monte Carlo (GCMC) and molecular dynamics (MD) techniques. The results reveal that the presence of water significantly enhances the adsorption of elemental mercury across different relative humidity levels. Detailed analyses of free energy and structural properties indicate a preference for water to occupy the corners of tetrahedral cages in UiO-66. Here, water exhibits stronger interactions compared to Hg 0 , which predominantly occupies the tetrahedral cages. Moreover, MD simulations demonstrate that while Hg 0 ′s self-diffusion coefficient remains stable at lower water loadings, it decreases dramatically at higher loadings (32 molecules per supercell) due to clustering effects that impede diffusion. Further analysis of the velocity autocorrelation functions shows that, at elevated water loadings, the rapid clustering of water significantly affects the motion of Hg 0 .