Fabricating a Robust Ultramicroporous Metal-Organic Framework for Purifying Natural Gas and Coal Mine Methane

Purifying methane (CH₄) from natural gas and coal mine methane (CMM) is of great significance but challenging in the chemical industry. Herein, a robust ultramicroporous metal-organic framework (MOF) is reported, which can be synthesized on a gram scale by stirring under room temperature. Single-component adsorption isotherms of gases (CH₄, ethane (C₂H₆), propane (C₃H₈), nitrogen (N₂)) and breakthrough experiments indicate that the MOF can separate CH₄ efficiently from CH₄/C₂H₆/C₃H₈ ternary mixture, with super high purity-CH₄ production of 154.7 cm³ g⁻¹. Additionally, the MOF shows higher CH₄ capacity than N₂, resulting in excellent separation performance for the CH₄/N₂ mixture. Notably, the binding sites of gases can be precisely determined by single-crystal X-ray data, further confirmed by molecular simulation. It is found that there are multiple hydrogen bonds and C─H···π interactions between the gases and the framework. This work offers an excellent candidate material for CH₄ purification with both high capacity and separation efficiency.