Scalable Copper-Based Coordination Frameworks with Tailored Pore Chemistry for Energy-Efficient C2H2/CO2 Separation

The separation of C2H2/CO2 mixtures for acetylene purification presents both industrial significance and fundamental challenges due to their nearly identical kinetic diameters and similar physical properties. This study demonstrates the effectiveness of ultramicroporous metal-organic frameworks (MOFs) in addressing this challenge through precise pore confinement effects. We report two ultramicroporous porous materials: Cu(cyhdc) (cyhdc2- = trans-1,4-cyclohexanedicarboxylate) and Cu(bdc) (bdc2- = 1,4-benzenedicarboxylate) and investigated their performance of capturing C2H2. At ambient conditions, both materials exhibit high C2H2 sorption capacities (1.92mmol g-1 for Cu(cyhdc) and 1.44mmol g-1 for Cu(bdc)). The most promising candidate is Cu(cyhdc), which shows decent C2H2 uptake capacity and a pretty high C2H2/CO2 selectivity (8.45 at 298K and 1 bar). Grand canonical Monte Carlo simulations revealed that the enhanced performance originates from multiple van der Waals interactions between C2H2 molecules and the curved cyclohexane-derived pore walls of Cu(cyhdc). Importantly, dynamic breakthrough experiments and scalable synthesis processes validated the practical separation potential of Cu(cyhdc) for C2H2/CO2 mixtures. This work provides both mechanistic insights into gas-framework interactions and a potential solution for energy-efficient acetylene purification.