One-Step Ethylene Purification by an Ethane-Screening Metal-Organic Framework.

Abstract

Efficient purification of ethylene (C2H4) from ethane (C2H6) is a crucial but daunting task for the chemical industry given their similar physical natures and molecular dimensions. Reversed capture of C2H6 from C2H6/C2H4 dual-mixtures can be expected to directly yield high-purity C2H4 through a one-step separation unit, but it remains a daunting challenge. Here, we skillfully target an unusual "electrostatic-driven linker microrotation" (EDLM) in a Zr-MOF through coupling dual-ligands having electron-withdrawing/donating groups (e.g., F and CH3 motifs). EDLM triggered microrotation of linker geometry and screening sites not only enhanced structural rigidity and hydrophobic nature, etc., but also effectively purified C2H4 through reversely trapping C2H6. Under ambient conditions, 1 kg of activated 2 adsorbents directly produces 7.2 L of C2H4 with over 99.9%+ purity in a single breakthrough operation starting from the equimolar C2H6/C2H4 cracked mixtures. Geometrical models and simulations have revealed that EDLM-derived H-bonding interaction and microrotation of linker geometry, synergistically customized C2H6-selective screening sites and pore inert for reversed C2H6 capture and improved surface hydrophobicity. Adsorption isotherms, modeling simulations, and breakthrough tests based on pressure swing adsorption (PSA) conditions have jointly elucidated the underlying separation properties for C2H4 purification. The enhanced hydrophobic nature, cycling durability, and separation property awarded 2 a new benchmark adsorbent to purify the olefin/paraffin mixtures.