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

Abstract

ABSTRACT Adsorption‐based processes offer an efficient approach for the treatment of ventilation air methane (VAM). However, existing separation mechanisms typically distinguish CH 4 and N 2 based on their insignificant differences in polarizability and size, and remain largely ineffective for VAM with extremely low CH 4 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 CH 4 , realizing precise CH 4 recognition. The clathrate‐like methane trap exhibited a high isosteric heat of adsorption ( Q st ) of 36.0 kJ mol −1 for CH 4 , a benchmark Q st difference between CH 4 and N 2 (19.6 kJ mol −1 ), and the highest reported equilibrium‐kinetic combined selectivity (19.0). Breakthrough experiments confirmed that this trap efficiently captured CH 4 from a CH 4 /N 2 (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 CH 4 could be obtained from a CH 4 /N 2 (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 CH 4 affinity.