Adsorption of hydrogen in covalent organic frameworks using expanded Wang–Landau simulations

Abstract

Using expanded Wang–Landau simulations, we study the adsorption of hydrogen in a series of covalent organic frameworks (COF-102, COF-105 and COF-108). In the present implementation, this new method, based on the Wang–Landau sampling, allows for a uniform sampling of the number of molecules adsorbed in the COFs. We show that this method leads to a highly accurate estimate of the grand canonical partition function for the system and gives excellent results for the adsorption isotherms of , both at and , when compared to prior simulation work and experiments. Moreover, various thermodynamic properties of adsorption, including entropy, Gibbs free energy and Helmohltz free energy, as well as the desorption properties are calculated, providing insight into the adsorption phenomenon. We finally propose a ranking for the performance of the three COFs for adsorption, based on the isothermal work required to regenerate the adsorbent , and find the following order for applications at ambient temperature.

Keywords::

• adsorption
• expanded Wang–Landau simulations
• covalent organic frameworks
• hydrogen storage
• thermodynamic properties

Acknowledgements

Partial funding for this research was provided by NSF through CAREER award DMR-1052808.