Adsorption and diffusion of H₂ , N₂ and H₂ / N₂ in Zeolitic Imidazolate Framework-67 by advanced computational calculations

Abstract

ZIF-67 (Zeolitic Imidazolate Framework-67) is a class of porous materials which have applications as catalysis, gas storage and gas separation. ZIF-67 consists of Cobalt (Co) connected to Methylimidazolate (MeIM). In this work, Gibbs Ensemble Monte Carlo (GEMC) simulations and Molecular Dynamics (MD) simulations were carried out to study adsorption behavior, structural and dynamics properties of Hydrogen (H₂) and Nitrogen (N₂) in ZIF-67 at three temperatures. The adsorption isotherms results indicate that ZIF-67 can adsorb N₂ in higher amount than H₂. The amount adsorbed decreases with the increase in temperatures. The different sets of Co force field parameters do not significantly affect the gas adsorption, except at lower temperatures. From the Radial Distribution Functions (RDFs), the preferential adsorption site for H₂ and N₂ is around the organic linker zone. N₂ binds stronger than H₂. In order to observe the dynamics behavior of gases, the self-diffusion (Ds) was calculated. It was found that Ds of N₂ is the lower than Ds of H₂. That means N₂ moves slower than H₂. Finally, it can be concluded that ZIF-67 is well suited to separate H₂ from N₂.