Hierarchical porosity and tailored surface functionality synergism enabling high-selectivity and capacity CH₄/N₂ separation for coalbed methane purification

Effective separation of low-concentration CH₄/N₂ mixtures is essential for coalbed methane purification and clean energy utilization. However, current adsorptive separation technology encounters a significant challenge because CH₄ (3.8 Å) and N₂ (3.6 Å) have similar kinetic diameters, and there are limited porous materials both possessing adsorption capacity and selectivity on their own. Here, we rational design an efficient porous composites material to realize selective adsorption of CH₄ and hinder N₂ diffusion, where hierarchical pore architecture of activated carbon (AC) provides abundant adsorption sites, and the bromine-functionalized metal organic framework (MOF) enhances surface polarity and tailors the pore environment. Thus, UiO-66-Br₂@AC exhibits the excellent performance, with a CH₄/N₂ selectivity of 8.94 at 298 K and a CH₄ uptake of 1.16 mmol·g⁻¹. Breakthrough experiments confirmed its high separation efficiency under dilute conditions (CH₄/N₂ = 10/90, v/v), and excellent cycling durability. This study presents a powerful approach for natural gas purification.