Ionic Liquid/Metal–Organic Framework Composites for H₂S Removal from Natural Gas: A Computational Exploration

Abstract

The separation of H₂S/CH₄ mixture was computationally examined in the composites of ionic liquids (ILs) supported on metal–organic frameworks (MOFs) at room temperature. Cu-TDPAT was selected as supporter for four types of ILs combined from identical cation [BMIM]⁺ with different anions ([Cl]⁻, [Tf₂N]⁻, [PF₆]⁻, and [BF₄]⁻). The results show that introducing ILs into Cu-TDPAT can greatly enhance the adsorption affinity toward H₂S compared to the pristine MOF, and the strongest enhancement occurs in the composite containing the anion [Cl]⁻ with the smallest size. The H₂S/CH₄ adsorption selectivities of each composite are significantly higher than those of the pristine Cu-TDPAT within the pressure range examined, and the selectivity generally shows an increasing trend with increasing the loading of the IL. By further taking the H₂S working capacity into account, this work also reveals that the [BMIM]­[Cl]/Cu-TDPAT composite exhibits the best separation performance in both VSA and PSA processes. These findings may provide useful information for the design of new promising IL/MOF composites applied for H₂S capture from natural gas