Achieving Record C₂H₂ Packing Density for Highly Efficient C₂H₂/C₂H₄ Separation with a Metal-Organic Framework...

Adsorptive C₂H₂/C₂H₄ separation using metal-organic frameworks (MOFs) has emerged as a promising technology for the removal of C₂H₂ (acetylene) impurity (1 %) from C₂H₄ (ethylene). The practical application of these materials involves the optimization of separation performance as well as development of scalable and green production protocols. Herein, we report the efficient C₂H₂/C₂H₄ separation in a MOF, Cu(OH)INA (INA: isonicotinate) which achieves a record C₂H₂ packing density of 351 mg cm^-3 at 0.01 bar through high affinity towards C₂H₂. DFT (density functional theory) calculations reveal the synergistic binding mechanism through pore confinement and the oxygen sites in pore wall. The weakly basic nature of binding sites leads to a relatively low heat of adsorption (Q_st) of approximately 36 kJ/mol, which is beneficial for material regeneration and thermal management. Furthermore, a scalable and environmentally friendly synthesis protocol with a high space-time yield of 544 kg m^-3 day^-1 has been developed without using any modulating agents. This material also demonstrates enduring separation performance for multiple cycles, maintaining its efficacy after exposure to water or air for three months.