A scalable and robust metal–organic framework with encircling hydrogen-bonding nanopockets for effective coal-bed methane purification

In the industrial field, building suitable adsorbents capable of enriching and purifying methane (CH₄) from coalbed methane is a necessary but challenging task. Herein, we selected a robust and scalable manganese-based metal–organic framework (Mn-TAZ) with suitable channel sizes and encircling hydrogen-bonding nanopockets, which are benefit to preferentially capture CH₄ over N₂. Mn-TAZ showed a high volumetric adsorption for CH₄ of 39.2 cm³ cm⁻³ at 298 K and 1.0 bar, and a good adsorption selectivity for CH₄/N₂ mixture. The separation mechanisms revealed by grand canonical Monte Carlo simulations and density functional theory calculations are mainly attributed to the appropriate nanopockets and the large number of exposed N atoms in the one-dimensional channels in Mn-TAZ, which have a greater affinity for CH₄ than N₂. Dynamic breakthrough experiments conducted under ambient conditions indicate that Mn-TAZ has great potential for the practical separation of CH₄/N₂, which is promising for application in relevant industrial processes. In addition, it is expected to enable large-scale batch synthesis in the industrial field by adjusting the initial feed amount to achieve scaled-up production. Both experiments and theoretical calculations clearly show that the strategy of constructing hydrogen-bonding nanopockets and abundant binding sites within MOFs is a feasible method to achieve efficient separation of CH₄/N₂. This work provides useful insights for the development of high-efficiency MOF adsorbents to solve intractable industrial separation challenges.