(551e) Molecular Modeling of Adsorption of CO2 and Water in Hydrophobic Metal-Organic Frameworks

Authors: 
Snurr, R. Q. - Presenter, Northwestern University
Zhang, H., Northwestern University
Moghadam, P. Z., Northwestern University
Materials having hydrophobic nanopores are potentially useful for selectively adsorbing molecules of interest out of aqueous solution or from the humid atmosphere. This talk will focus on recent molecular-level modeling of CO2 and water in hydrophobic metal-organic frameworks (MOFs). First, we focus on adsorption of CO2, water, and their mixtures in the flexible, hydrophobic MOF known as FMOF-1. A combination of simulation and various experimental measurements provide a unified picture of unusual isotherm shapes in this material, resulting from framework flexibility and progressive filling of adsorption sites with increasing pressure. We also report a case study of the difficulties in simulating adsorption isotherms for water in ZIF-8, another hydrophobic MOF, where the simulations take a very long time to equilibrate. Based on insights obtained about the adsorption mechanism, we investigated several advanced Monte Carlo algorithms including energy-bias moves and continuous fractional component Monte Carlo (CFC MC) and were able to accelerate the simulation speed by a factor of 6.7 over the conventional grand canonical Monte Carlo algorithm. The insights obtained from this work may also help improve the molecular simulation efficiency for studies of water adsorption in other hydrophobic materials.