A cobalt metal-organic framework with small pore size for adsorptive separation of CO₂ over N₂ and CH₄

In this study, a new cobalt-based metal-organic framework (MOF), [(Formula presented.) (μ₃-OH)₂(ipa)₅(C₃O₂)(DMF)₂] (CoIPA) was synthesized. The crystal structure analysis shows that CoIPA is constructed by Co₆(μ₃-OH)₂ units linked by isophthalic acid forming a sxb topology and it possesses a small pore size of about 4 Å. The new MOF has been characterized using multiple experimental methods. Monte Carlo and Molecular Dynamic simulations were employed to investigate adsorption equilibrium and kinetics in terms of capacity and diffusivity of CO₂, N₂, and CH₄ on CoIPA. The gas adsorption isotherms collected experimentally were used to verify the simulation results. The activated CoIPA sample exhibits great gas separation ability at ambient conditions for CO₂/N₂ and CO₂/CH₄ with selectivity of around 61.4 and 11.7, respectively. The calculated self-diffusion coefficients show a strong direction dependent diffusion behavior of target molecules. This high adsorption selectivity for both CO₂/N₂ and CO₂/CH₄ makes CoIPA a potential candidate for adsorptive CO₂ separation.