Microporous Metal-Organic Frameworks with Hydrophilic and Hydrophobic Pores for Efficient Separation of CH₄/N₂...

Highly selective removal of N₂ from unconventional natural gas is considered as a viable way to increase the heat value of CH₄ and reduce the greenhouse effect caused by the direct emission of CH₄/N₂ mixture. In this work, a three-dimensional Cu-MOF with two different types of micropores was synthesized, exhibiting a high selectivity for CH₄/N₂ (10.00-12.67) and the highest sorbent selection parameter value (65.73) among the reported materials. The CH₄ molecule interacts with the framework to form multiple van der Waals interactions both in hydrophilic and hydrophobic pores, indicated by density functional theory calculations to gain a deep insight into the adsorption binding sites. In contrast, the weak polarity feature of the hydrophobic pore and the occupied open-metal sites in the hydrophilic pore result in a very low adsorption uptake of N₂. The excellent separation performance combining the good stability and regenerability guarantees this Cu-MOF to be a promising adsorbent for an efficient separation of the CH₄/N₂ mixture.