C ₂ H ₂ /CO ₂ Separation by a Carborane Hybrid 2D Metal–Organic Framework

The separation of acetylene (C₂H₂) from carbon dioxide (CO₂) is important in industry but challenging due to their similar physical properties. Herein, a boron-rich 2D metal-organic framework ZNU-14 based on the carborane backbone was readily prepared by the supramolecular assembly of Zn²⁺, <i>p</i>-C₂B₁₀H₁₀-(COOH)₂, and di(pyridin-4-yl) amine under mild conditions for C₂H₂/CO₂ separation. ZNU-14 displays a straight 1D channel (7.6 × 12.5 Ų) with an electronegative pore surface. Gas adsorption isotherms show that ZNU-14 has a good C₂H₂ adsorption capacity of 43.6 cm³ g^-1, 181% of the CO₂ uptake capacity. The calculated ideal adsorbed solution theory (IAST) selectivity is as high as 6.3-9.7, outperforming many popular materials. The moderate C₂H₂ adsorption heat of 34.3 kJ mol^-1 facilitates the straightforward desorption and regeneration of ZNU-14. Furthermore, the theoretical study confirmed the stronger binding of C₂H₂ compared to that of CO₂. The practical C₂H₂/CO₂ separation performance was fully demonstrated by breakthrough experiments with excellent dynamic selectivity and recyclability under various conditions.