Two-Dimensional Metal-Organic Framework with Ultrahigh Water Stability for Separation of Acetylene from Carbon...

Highly selective separation and purification of acetylene (C₂H₂) from ethylene (C₂H₄) and carbon dioxide (CO₂) are daunting challenges in light of their similar molecule sizes and physical properties. Herein, we report a two-dimensional (2D) stable metal-organic framework (MOF), NUM-11 ([Cu(Hmpba)₂]·1.5DMF) (H₂mpba = 4-(3,5-dimethyl-1H-pyrazol-4-yl)benzoic acid), with sql topology, stacked together through π-π interactions for efficient separation of C₂H₂ from C₂H₄ and CO₂. The 2D-MOF material offers high hydrolytic stability and good purification capacity; especially, it could survive in water for 7 months, even longer. This stable MOF selectively captures C₂H₂ from mixtures containing C₂H₄ and CO₂, as determined by adsorption isotherms. The ideal adsorbed solution theory selectivity calculations and transient breakthrough experiments were performed to verify the separation capacity. The low isosteric heat of NUM-11a (desolvated NUM-11) (18.24 kJ mol^-1 for C₂H₂) validates the feasibility of adsorbent regeneration with low energy footprint consumption. Furthermore, Grand Canonical Monte Carlo simulations confirmed that the pore surface of the NUM-11 framework enabled preferential binding of C₂H₂ over C₂H₄ and CO₂ via multiple C-H···O, C-H···π, and C-H···C interactions. This work provides some insights to prepare stable MOF materials toward the purification of C₂H₂, and the water-stable structure, low isosteric heat, and good cycling stability of NUM-11 make it very promising for practical industrial application.