"Two-in-One" Anion Engineering Strategy for One-Step Ethylene Purification From a Ternary Mixture

One-step purification of C₂H₄ from a C₂H₂/CO₂/C₂H₄ mixture represents a significant industrial challenge. However, conventional ligand engineering strategies struggle to simultaneously enhance adsorption capacity and separation selectivity. Herein, we present an innovative "two-in-one" anion engineering strategy involving the substitution of SiF₆ ^2- with ZrF₆ ^2-, which enhances CO₂ capture while effectively shields C₂H₄ adsorption at the fluorine sites. Compared to SIFSIX‑1‑Cu‑(CH₃)₂, ZrFSIX‑1‑Cu‑(CH₃)₂ exhibits a dramatically enhanced CO₂ uptake (from 35.3 to 87.3 cm³/g). More importantly, the adsorption preference shifts from C₂H₄-selective to CO₂-selective, with the CO₂/C₂H₄ (50/50) ideal adsorbed solution theory (IAST) selectivity increasing from 0.59 to 1.66. Dynamic breakthrough experiments demonstrate the exceptional separation performance of ZrFSIX‑1‑Cu‑(CH₃)₂ for a C₂H₂/CO₂/C₂H₄ (1/9/90) mixture. Theoretical calculations reveal that the highly electronegative F atoms on the ZrF₆ ^2- anions enhance the interactions with CO₂, while ligand rotation-induced pore contraction and methyl steric effects act synergistically to hinder C₂H₄ from accessing the fluorine sites. This study provides a new paradigm for the design of materials aimed at purifying C₂H₄ from multi-component mixtures.