This study employs grand canonical Monte Carlo (GCMC) simulations to investigate the impact of functional group modifications (CH3, OH, NH2, and OLi) 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.
Keywords: CH4 adsorption; CH4/N2 adsorption separation; MOF materials; grand canonical Monte Carlo.
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