Optimizing Charge Separated Synergistic Binding Sites in Self-Healing Crystalline Porous Organic Salts for Benchmark Trace Alkyne/Alkene Separation

Abstract

The separation of trace alkyne (C₂H₂/C₃H₄) impurities from alkenes (C₂H₄/C₃H₆) is a significant but challenging process to produce polymer-grade C₂H₄ and C₃H₆. Herein, we reported an optimally designed charge-separated organic framework, crystalline porous organic salt (CPOS-1), with confined polar channels for highly efficient alkyne/alkene separation. CPOS-1 exhibits excellent stability, remarkably high C₂H₂ (18.4 cm³ g⁻¹) and C₃H₄ (20.9 cm³ g⁻¹) uptakes at 0.01 bar and 298 K, and benchmark C₂H₂/C₂H₄ (25.1) and C₃H₄/C₃H₆ (43.9) separation selectivities for 1/99 alkyne/alkene mixtures. The practical alkyne/alkene separation performance was completely identified by breakthrough-column experiments under various conditions with excellent cycle stability and high alkene productivities (C₂H₄: 216.6 L kg⁻¹; C₃H₆: 162.4 L kg⁻¹). Theoretical calculations indicated that pore aperture in CPOS-1 acts as a tailored single-molecule trap, where alkynes are captured by multiple synergistic electropositive and electronegative sites, thus enhancing alkyne recognition. Furthermore, the ease of rehealing facilitates its practical application, transcending the limitations of the metal-organic frameworks (MOFs) and covalent organic frameworks (COFs).