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.