Development of Nix/Mg1−x-MOF-74 for highly efficient CO2/N2 separation
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Abstract
To enhance the separation selectivity of Mg-MOF-74 towards CO2 in a CO2/N2 mixture, a series of Mg-MOF-74 and Nix/Mg1−x-MOF-74 adsorbents were prepared by solvothermal synthesis in this paper. It was found that the adsorption capacity of Mg-MOF-74 for CO2 could be effectively increased by optimizing the amount of acetic acid. On this basis, the bimetal MOF-74 adsorbent was prepared by metal modification. The multi-component dynamic adsorption penetration analysis was utilized to examine the CO2 adsorption capacity and CO2/N2 selectivity of the diverse adsorbent materials. The results showed that Ni0.11/Mg0.89-MOF-74 showed a CO2 adsorption capacity of 7.02 mmol/g under pure CO2 atmosphere and had a selectivity of 20.50 for CO2/N2 under 15% CO2/85% N2 conditions, which was 10.2% and 18.02% higher than that of Mg-MOF-74 respectively. Combining XPS, SEM and FT-IR characterization analysis, it was attributed to the effect of the more stable unsaturated metal sites Ni into the Mg-MOF-74 on the pore structure and the synergistic interaction between the two metals. Density Functional Theory (DFT) simulations revealed that the synergistic interaction between modulated the electrostatic potential strength and gradient of the material, which was more favorable for the adsorption of CO2 molecules with small diameters and large quadrupole moment. In addition, the Ni0.11/Mg0.89-MOF-74 showed commendable cyclic stability, underscoring its promising potential for practical applications.
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