Simulation study on functional group-modified Ni-MOF-74 for CH₄/N₂ adsorption separation

This study employs grand canonical Monte Carlo (GCMC) simulations to investigate the impact of functional group modifications (CH₃, OH, NH₂, and OLi) on the adsorption performance of CH₄/N₂ on Ni-MOF-74. The results revealed that functional group modifications significantly increased the adsorption capacity of Ni-MOF-74 for both CH₄ and N₂. The packed methyl groups in CH₃-Ni-MOF-74 create an environment conducive to CH₄, leading to the highest CH₄ adsorption capacity. The electrostatic potential distribution indicates that the strong electron-donating effect introduced by the alkali metal Li results in the highest electrostatic potential gradient in Li-O-Ni-MOF-74, leading to the strongest adsorption of N₂, this is unfavorable for CH₄/N₂ separation. At 1500 kPa the selectivity order of adsorbents for mixed gases was as follows: CH₃-Ni-MOF-74 > NH₂-Ni-MOF-74 > OH-Ni-MOF-74 > Ni-MOF-74 > Li-O-Ni-MOF-74. This study highlights that CH₃-Ni-MOF-74 possesses optimal CH₄ selectivity and adsorption performance. Given the current lack of research on functionalized MOF-74 for the separation of CH₄ and N₂, the findings of this study will serve as a theoretical guide and provide references for the applications of CH₄ adsorption and CH₄/N₂ separation.