Revving Up a Designed Copper Catecholate Porous Organic Polymer for Its Potent Ethylene Adsorption than Ethane

The potential to produce high-purity C₂H₄ has made ethylene-selective adsorbents for ethane (C₂H₆)/ethylene (C₂H₄) gas mixture separation appealing as viable substitutes for traditional cryogenic distillation. In this aspect, porous organic polymers (POPs) are anticipated to become the next-generation potential adsorbent due to their easily customizable functions and functional sites suitable for gas separation. This article reports the selective C₂H₄ adsorption over C₂H₆ using microporous copper(I)-coordinated POP (Cu@Di-POP) via fine-tuning of the π complexation and pore size. The specially designed adsorbent has the ideal pore size and coordinated Cu(I) ions to form π-complexation with C₂H₄ molecules, which enabled it to adsorb C₂H₄ (at 1 bar, 24.9, 18.9, and 13.4 cm³ g^-1 at 273, 298, and 323 K, respectively) while significantly reducing C₂H₆ adsorption (at 1 bar, 16.9, 12.7, and 8.8 cm³ g^-1 at 273, 298, and 323 K, respectively). At 1 bar, Cu@Di-POP exhibited IAST selectivities of 6.09, 5.60, and 4.13 for C₂H₄/C₂H₆ at 273, 298, and 323 K, respectively, suggesting its C₂H₄ selective behavior, which was further confirmed from the experimental breakthrough measurement. Furthermore, the computational studies carried out with density functional theory highlighted an enhanced charge distribution leading to dπ-pπ conjugation between C₂H₄ π-electrons and Cu d-electrons, thereby showing a relatively higher interaction energy of -37.23 kcal/mol with C₂H₄ as compared to -16.06 kcal/mol with C₂H₆ gas molecules.