Efficient C₂H₂ Separation from CO₂ and CH₄ within a Microporous Metal–Organic Framework of Multiple Functionalities

Abstract

The separation of acetylene (C2H2) from carbon dioxide (CO2) and methane (CH4) is of great significance, but remains challenging, because of their similar physicochemical properties, and it currently has received substantial research interest by using adsorptive separation based on metal–organic frameworks (MOFs). Herein, a new microporous Cu-MOF, [Cu(5-OH-IPA2–)(DPYA)(H2O)] (BUT-318, where 5-OH-IPA2– = 5-hydroxyisophthalate and DPYA = 4,4′-dipyridylamine) has been synthesized successfully under solvothermal conditions, which exhibits excellent separation performance for C2H2/CO2 and C2H2/CH4 gas mixtures. The presence of Cu(II) open metal sites and different Lewis base sites (−OH and −NH) make the activated BUT-318 efficiently bind C2H2 and exhibit high adsorption capacity under low pressure (24.52 and 9.1 cm3 g–1 under 0.01 bar, at 273 and 298 K, respectively). The corresponding IAST (ideal adsorbed solution theory) selectivity was 9.8 and 244.3 at 273 K and 1 bar for an equimolar C2H2/CO2 and C2H2/CH4 mixture. The separation performance and reusability under dynamic conditions were also confirmed by column breakthrough experiments, making BUT-318a a promising candidate for the practical C2H2 separation.