Predictions of Hg0 and HgCl2 Adsorption Properties in UiO-66 from Flue Gas Using Molecular Simulations

Adsorption of mercury species in porous materials is an attractive means to capture these species from flue gas, but the lack of reliable force fields (FFs) for Hg0 and HgCl2 has made modeling adsorption of these important species challenging. We introduce a robust set of FFs to describe interactions between Hg0, HgCl2, and other flue gas components and UiO-66, a prototypical metal–organic framework. Using these FFs, adsorption isotherms in UiO-66 for pure components and mixtures of Hg0, HgCl2, N2, CO2, and SO2 were simulated. HgCl2 has a strong affinity for UiO-66, with a heat of adsorption of ∼60 kJ/mol, whereas Hg0 is only weakly adsorbed. Critically, HgCl2 competes strongly with adsorption of CO2; we give illustrative examples where concentrations of HgCl2 as low as 1 ppm strongly diminish the selectivity and uptake of UiO-66 for CO2 that would be expected for a clean flue gas mixture. These results highlight the potential importance of even trace levels of HgCl2 in consideration of nanoporous adsorbents for CO2 capture in practical settings.