One Scalable and Stable Metal–Organic Framework for Efficient Separation of CH₄/N₂ Mixture

Separating CH₄ from coal bed methane is of great importance but challenging. Adsorption-based separation often suffers from low selectivity, poor stability, and difficulty to scale up. Herein, a stable and scalable metal–organic framework [MOF, CoNi(pyz-NH₂)] with multiple CH₄ binding sites was reported to efficiently separate the CH₄/N₂ mixture. Due to its suitable pore size and multiple CH₄ binding sites, it exhibits excellent CH₄/N₂ selectivity (16.5) and CH₄ uptake (35.9 cm³/g) at 273 K and 1 bar, which is comparable to that of the state-of-the-art MOFs. Theoretical calculations reveal that the high density of open metal sites and polar functional groups in the pores provide strong affinity to CH₄ than to N₂. Moreover, CoNi(pyz-NH₂) displays excellent structural stability and can be scale-up synthesized (22.7 g). This work not only provides an excellent adsorbent but also provides important inspiration for the future design and preparation of porous adsorbents for separations.