C2H2/CO2 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+, p-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 Å2) 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.