Regulating Layer Organization to Engage Amino Groups for Efficient CH₄/N₂ Separation in a Pillar-Layer Metal-Organic...

Selective capture of methane (CH₄) from nitrogen (N₂) in coal-bed methane using a physisorbent represents a promising strategy due to its potential for low energy consumption and cost-efficiency. Microporous metal-organic frameworks (MOFs) offer considerable potential for this application through tunable pore design, yet they face unresolved challenges including stability, low-cost synthesis, and adsorption durability. Herein, we demonstrate the effective capture of CH₄ from N₂ via a microporous zinc-aminotriazolate-acetate (Zn-Atz-Ac) framework. Employing zinc, acetate, and 3-amino-1,2,4-triazole, Zn-Atz-Ac is synthesized through an atom-economical route. Owing to a tortuous pore structure with numerous pockets containing abundant accessible nitrogen and oxygen sites, this material exhibits a CH₄ uptake of 25.18 cm³ g^-1 (298 K and 100 kPa) with a high CH₄/N₂ selectivity of 7.8. Notably, Zn-Atz-Ac maintains robust structural integrity and adsorption performance over five consecutive adsorption-desorption cycles. In contrast, an oxalate-pillared analogue Zn-Atz-OX exhibits a much lower CH₄ uptake of 18.2 cm³ g^-1 and a lower selectivity of 3.3 due to a less functionalized pore environment. Theoretical calculations reveal that the amino-rich pore environment in Zn-Atz-Ac contributes to its stronger preference for CH₄. Finally, breakthrough experiments confirm the effectiveness of Zn-Atz-Ac for CH₄/N₂ separation under dynamic conditions, demonstrating practical utility.