Understanding the Effective Capture of H<sub>2</sub>S/CO<sub>2</sub> from Natural Gas Using Ionic Liquid@MOF Composites
Weiqun Gao, Weizhong Zheng, Weizhen Sun, Ling Zhao
Abstract
Ionic liquids (ILs)/metal–organic framework (MOF) composites with unprecedented (CO2 and H2S)/CH4 selectivity are promising in producing high-quality natural gas for energy. Herein, the adsorption and separation of CO2/H2S/CH4 on a series of IL-incorporated MOF-108 materials were studied by Grand Canonical Monte Carlo (GCMC), molecular dynamic (MD), and density functional theory (DFT). The results indicate that MOF-108 remains stable after incorporating ILs. The IL/MOF composites with a stronger affinity to sorbate molecules can boost the acid gas capture ability and weaken the undesired methane adsorption. Furthermore, the choline-based amino acid IL/MOF composites generally show excellent separation performance due to the polarizable nature of ILs and the suitable annular space formed between IL and MOF-108. DFT analysis suggests that ILs can act as new adsorption sites for H2S and CO2. The IL in MOF-108 greatly boosts the framework attraction to H2S, thus making H2S more competitive for the adsorption sites of the IL/MOF frameworks than CO2. Finally, the results show that15 wt % [Chl][Ala]/MOF composite exhibits excellent (H2S and CO2)/CH4 selectivity of about 735% higher than the original MOF.