Maximizing acetylene packing density for highly efficient C₂H₂/CO₂ separation through immobilization of amine sites within a prototype MOF

For practical separation applications, porous sorbents with high separation performance, low heat of adsorption, high stability and low production cost are highly desired. A plausible strategy is herein developed through immobilization of amine sites in a prototype MOF for maximized packing density and selectivity. The CAU-10-NH₂ material exhibits high packing density of 0.46 cm³/g, C₂H₂ adsorption capacity (4.1 mmol/cm³, at 0.5 bar), and high C₂H₂/CO₂ selectivity of 10.8, which outperformed the unfunctionalized benchmark material CAU-10-H. Neutron powder diffraction study reveals the formation of densely packed C₂H₂ as tetrameric clusters in the pore. The separation performance of CAU-10-NH₂ well remains in column separation conditions, with a remarkable dynamic selectivity of 10.9. The good water-stability and one-step synthesis from commercially available precursors make this material a promising candidate for practical C₂H₂/CO₂ separation.