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 (Qst) of 36.0 kJ mol-1 for CH4, a benchmark Qst 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.
Zhang et al. (Thu,) studied this question.