Can Charge‐Modulated Metal‐Organic Frameworks Achieve High‐Performance CO₂ Capture and Separation over H₂, N₂, and CH₄?

Abstract

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.

A Molecular Dynamics Study Employing Bimetallic Co–CuHAB Nanosheets for Seawater Desalination

“…For example, in the theoretical study by Mortazavi et al, Co-, Cr-, Fe-, Mn-, Ni-, Pd-, and Rh-HAB nanosheets were discovered to exhibit linear elasticity with considerable tensile strength, with the Co-HAB nanosheet being the strongest material among the seven MOF nanosheets . Furthermore, physical studies have reported that Co-HAB is an excellent high-power energy storage material due to its high density, electrical conductivity, and chemical stability. − Meanwhile, studies on Cu-HAB have shown that it exhibits greater chemical stability than conventional MOFs in acidic and basic aqueous solutions . Notably, the Seebeck coefficient of Cu-HAB is almost 2 orders of magnitude higher than that of Co-HAB, and the high electrical conductivity of the former allows it to serve as an effective solo electrode. , …”