One-Step Ethylene Purification from a Seven-Component Cracking Gas Mixture with Sorbent-Sorbate Induced-Fit

Industrial purification processes for ethylene from steam pyrolysis or cracking gases generally employ multiple energy-intensive steps to remove C₂H₂, C₂H₆, CO₂, and C₃ hydrocarbons. Designing multifunctional molecular separators that integrate multiple structural characteristics capable of removing several impurities simultaneously is highly desired but not yet realized. Here, we address this challenge using a custom-designed multifunctional, and industry-compatible ultramicroporous crystalline physisorbent (CALF-20) to purify C₂H₄ from a seven-component cracking gas mixture (C₂H₄, C₂H₂, C₂H₆, CO₂, C₃H₄, C₃H₆, and C₃H₈) by one-step separation with remarkable performance. Verified by breakthrough experiments, C₂H₄ (>99.99 can be recovered not only from binary C₂H₆/C₂H₄ (50/50), ternary C₂H₂/C₂H₄/C₂H₆ (33/33/33), and quaternary C₂H₂/C₂H₄/C₂H₆/CO₂ (25/25/25/25) mixtures, but also from a typical seven-component gas cracking mixture of C₂H₂/C₂H₄/C₂H₆/CO₂/C₃H₄/C₃H₆/C₃H₈ (0.6/62/10/0.3/0.6/26/0.5), even at the high humidity of 74 CALF-20 can be easily produced on the kilogram scale, showing great commercial application potential. Together with its framework flexibility and appropriate pore geometry, CALF-20 exhibits a sorbent-sorbate induced-fit behavior strengthening multiple specific recognition sites for the corresponding guests, validated by single-crystal X-ray diffraction study and molecular modeling. This work is the first example of using a single physisorbent to purify C₂H₄ from a seven-component cracking gas mixture and opens an avenue to address complicated hydrocarbon mixture separation challenges.