Can Charge-Modulated Metal-Organic Frameworks Achieve High-Performance CO₂ Capture and Separation over H₂ , N₂ , and...

CO₂ capture and separation by using charge-modulated adsorbent materials is a promising strategy to reduce CO₂ emissions. Herein, three TM-HAB (TM=Co, Ni, and Cu; HAB=hexa-aminobenzene) metal-organic frameworks (MOFs) were evaluated as charge-modulated CO₂ capture and separation materials by using density functional theory and grand canonical Monte Carlo simulations. The results showed that each TM-HAB presented a high electrical conductivity and structural stability when injecting charges. The CO₂ adsorption energy increased from 0.211 to 2.091 eV on Co-HAB, 0.262 to 2.119 eV on Ni-HAB, and 0.904 to 2.803 eV on Cu-HAB, respectively, with the increase in charge state from 0.0 to 3.0 e^- . Co-HAB and Ni-HAB were better charge-modulated CO₂ capture materials with less structure deformation based on energy decomposition analyses. The kinetic process demonstrated that considerably low energy consumptions of 0.911 and 1.589 GJ ton^-1 CO₂ were observed for a complete adsorption-desorption cycle on Co-HAB and Ni-HAB. All charged MOFs, especially Co-HAB and Ni-HAB, exhibited higher CO₂ adsorption energies and adsorption capacities than those of H₂ , N₂ , and CH₄ , thereby exhibiting high CO₂ selectivities. Interaction analysis confirmed that the injecting charges had a more pronounced enhancement in the coulombic interactions between CO₂ and MOFs. The results of this work highlight Co-HAB and Ni-HAB as promising charge-modulated CO₂ capture and separation materials with controllable CO₂ capture, high selectivity, and low energy consumption.