Selectivity adsorption mechanism of different phenolic organic pollutants on UiO-66 by molecular dynamics simulation

Metal organic frameworks (MOFs) as an excellent adsorbent have been widely utilized in wastewater treatment due to high specific surface area, high porosity, adjustable structure and surface functionability. To design MOFs materials based on the application for removal of pollutant, understand the adsorption mechanism between pollutant and MOFs from the microscopic scale is necessary but rare. Herein, UiO-66 is selected as the adsorbent to investigate the adsorption mechanisms with phenolic organic pollutants (POPs) on the microscopic scale via MD simulation. Equilibrium configuration and density distribution for three different POPs (phenol, nitrophenol and bisphenol) prove the adsorption behavior occurred on the surface of UiO-66. Obviously, the difference of adsorption capacity proves UiO-66 tends to adsorb the nitrophenol compared to other two molecules and has the lower adsorption capacity for bisphenol due to larger molecule size, and in a neutral environment, it is more conducive to be adsorbed than in an alkaline environment. Mean square displacement (MSD) and radial distribution functions (RDFs) further support this conclusion, which exhibit the introduction of -NO2 groups can enhance the interaction of host-guest. The H-bonds, pi-pi stacking and interaction energy between UiO-66 and POPs was quantificationally calculated, the results show Van der Waals and pi-pi stacking dominate adsorption between POPs and UiO-66.