(436e) Improving the Efficiency of Water Adsorption Simulations in Metal-Organic Frameworks

Water is one of the most common components in industrial gas or liquid systems. It often has a non-negligible effect on chemical and physical processes such as gas or liquid adsorption in porous materials, like zeolites and metal-organic frameworks (MOFs). Molecular modeling techniques, especially grand canonical Monte Carlo (GCMC) simulations, have been used by many researchers to study the adsorption of water in porous media and to obtain useful information about the molecular-level interactions. However, due to the high density and complex hydrogen bonding in water systems, these GCMC simulations usually suffer from very low probability of successful insertions, leading to extremely long simulation times especially in the high loading regime. To improve the simulation efficiency for these systems, we selected the hydrophobic MOF ZIF-8 as a representative adsorbent and tested the performance of multiple advanced simulation algorithms, including pre-tabulated energies (â??gridâ? method), energy-biased insertions, and continuous fractional component Monte Carlo (CFC MC) for water adsorption. We showed that these methods can improve the insertion and deletion probabilities and the simulation speed compared with conventional GCMC simulation. Furthermore, an alternative computational approach for calculating adsorption isotherms, using molecular dynamics simulations and computation of the chemical potential, was studied and applied to different adsorption systems including water. Some promising results and insights have been discovered for this new approach.