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

Highly selective removal of N-2 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/N-2 mixture. In this work, a three-dimensional Cu-MOF with two different types of micropores was synthesized, exhibiting a high selectivity for CH4/N-2 (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 openmetal sites in the hydrophilic pore result in a very low adsorption uptake of N-2. 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/N-2 mixture.