Efficient inverse CO2/C2H2 separation driven by difference in rare thermodynamic affinities in a porous MOF†

Separating C₂H₂ from CO₂ is crucial in the petrochemicals industry but extremely difficult, owing to their very close molecular sizes and similar physical characteristics. Herein, a new porous MOF with 1D rhombus channels featuring plentiful open metal sites was built. The activated framework presents a high CO₂ uptake of 83.1 cm³ cm⁻³ at 298 K under 100 kPa and uncommon inverse selectivity for the CO₂/C₂H₂ mixtures. What's more, the MOF can directly yield high-purity C₂H₂ (≥99.9%) from CO₂/C₂H₂ mixtures (v/v = 50/50 and 10/90) under ambient conditions through a single breakthrough separation process, which significantly increased the separation efficiency and reduced energy consumption. The GCMC simulations revealed that highly efficient inverse CO₂/C₂H₂ separation performance arose from the higher thermodynamic affinities for CO₂ than C₂H₂.