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

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 CPOS-1 with confined polar channels for highly efficient alkyne/alkene separation. CPOS-1 exhibits excellent stability, remarkably high C2H2 (18.4 cm3/g) and C3H4 (20.9 cm3/g) 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; C3H6: 162.4 L/kg). 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 the alkyne recognization. Furthermore, the ease of rehealing facilitates its practical application, transcending the limitations of the metal-organic frameworks (MOFs) and covalent organic frameworks (COFs).