A Clathrate-Like Methane Trap for Capture of Mine Ventilation Air Methane

Adsorption-based processes offer an efficient approach for the treatment of ventilation air methane (VAM). However, existing separation mechanisms typically distinguish CH₄ and N₂ based on their insignificant differences in polarizability and size, and remain largely ineffective for VAM with extremely low CH₄ concentrations. Here, we reported a clathrate-like methane trap featuring dense arrays of electronegative O/N atoms as in methane hydrate, which exhibited electrostatic potential and shape complementarity toward CH₄, realizing precise CH₄ recognition. The clathrate-like methane trap exhibited a high isosteric heat of adsorption (Q_st) of 36.0 kJ mol^-1 for CH₄, a benchmark Q_st difference between CH₄ and N₂ (19.6 kJ mol^-1), and the highest reported equilibrium-kinetic combined selectivity (19.0). Breakthrough experiments confirmed that this trap efficiently captured CH₄ from a CH₄/N₂ (1/99) mixture, providing a record-high breakthrough selectivity (3.8). Its practical potential was validated by conducting a two-bed, six-step, variable-pressure swing adsorption process, and 25% purity CH₄ could be obtained from a CH₄/N₂ (1/99) mixture. In situ infrared spectroscopy and computational modelling studies revealed that the rational arrangement of dense N/O binding sites imparted a synergy between optimal pore shape and surface electrostatic potential that boosted CH₄ affinity.