Organic Cage with Interconnected Aromatic Cavity‐Channel Pores for One‐Step Purification of Ethylene

Abstract Constructing a metal‐free adsorbent for one‐step separation of C₂H₄ from mixture gas of C2, is of great significance and challenging. Here, a porous aromatic cage (PAC‐1) based on aldehyde‐amine condensation is reported with diamond‐like interconnected aromatic cavity‐channel pores for one‐step purification of ethylene. PAC‐1 exhibits superior C₂H₂ (52.6 cm³ g⁻¹) and C₂H₆ (46.7 cm³ g⁻¹) uptakes as well as impressive C₂H₂/C₂H₄ selectivity (1.5) and C₂H₆/C₂H₄ selectivity (1.4), remaining at the forefront of the advanced C₂H₄‐selective adsorbents of porous non‐metallic materials. The C₂H₄ adsorption enthalpy (Q_st) of PAC‐1 is of 23.6 kJ mol⁻¹, which requires less energy to regenerate than conventional MOF materials. Breakthrough experiments demonstrate that PAC‐1 can reduce the penetration rate of C₂H₆ or C₂H₂ through the adsorbent, and present quite valuable one‐step separation of C₂H₄ from C₂H₂/C₂H₆/C₂H₄ mixture gas. Molecular simulations and DFT studies have shown that oxygen sites and C─H sites in the channels are more favorable for C₂H₂ anchor with interaction energy over C₂H₄ by 1.48 kcal mol⁻¹, and the C─H…π interaction point in cage cavity is preferred to C₂H₆ with the interaction energy over C₂H₄ by 1.16 kcal mol⁻¹, which in turn results in the separation of C₂H₄ from C₂H₂ and C₂H₆.