Exploiting equilibrium-kinetic synergetic effect for separation of ethylene and ethane in a microporous metal-organic framework

Abstract

Physisorption is a promising technology to cut cost for separating ethylene (C₂H₄) from ethane (C₂H₆), the most energy-intensive separation process in the petrochemical industry. However, traditional thermodynamically selective adsorbents exhibit limited C₂H₄/C₂H₆ selectivity due to their similar physiochemical properties, and the performance enhancement is typically at the expense of elevated adsorption heat. Here, we report highly-efficient C₂H₄/C₂H₆ adsorption separation in a phosphate-anion pillared metal-organic framework ZnAtzPO₄ exploiting the equilibrium-kinetic synergetic effect. The periodically expanded and contracted aperture decorated with electronegative groups within ZnAtzPO₄ enables effective trapping of C₂H₄ and impedes the diffusion of C₂H₆, offering an extraordinary equilibrium-kinetic combined selectivity of 32.4. The adsorption heat of C₂H₄ on ZnAtzPO₄ (17.3 to 30.0 kJ mol^-1) is substantially lower than many thermodynamically selective adsorbents because its separation capability only partially relies on thermodynamics. The separation mechanism was explored by computational simulations, and breakthrough experiments confirmed the excellent C₂H₄/C₂H₆ separation performance of ZnAtzPO₄.