Recent Advances in Adsorbents for CH₄/N₂ Separation: A Mini-Review

The kinetic diameters and polarizabilities of methane and nitrogen are nearly identical, resulting in the separation of CH4 and N2 being a huge challenge. This review provides a comprehensive overview of adsorbent materials, including porous carbon materials, zeolites, metal–organic frameworks (MOFs), and composite materials, used in the separation of CH4/N2. Especially, the latest research advances in modification techniques, adsorption kinetics, and adsorption mechanisms of the adsorbents are elucidated, which are the crucial factors for the improvement of their saturated adsorption capacity and selectivity. It is evident that the adsorbent materials with regular pore structures and a higher proportion of pore sizes <1 nm are more favorable for methane enrichment. Second, the low-polarity channels of the adsorbent material, in conjunction with the presence of specific functional groups and unsaturated metal sites, promote enhanced interactions between methane and the material. This, in turn, leads to superior adsorption performance. In all, this review aims to provide a reference point for the design and optimization of adsorbent materials for the separation of methane and nitrogen.