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

Highly selective separation and purification of acetylene (C 2 H 2 ) from ethylene (C 2 H 4 ) and carbon dioxide (CO 2 ) 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) (H 2 mpba = 4-(3,5-dimethyl-1 H -pyrazol-4-yl)benzoic acid), with sql topology, stacked together through π-π interactions for efficient separation of C 2 H 2 from C 2 H 4 and CO 2 . 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 C 2 H 2 from mixtures containing C 2 H 4 and CO 2 , 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 C 2 H 2 ) 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 C 2 H 2 over C 2 H 4 and CO 2 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 C 2 H 2 , and the water-stable structure, low isosteric heat, and good cycling stability of NUM - 11 make it very promising for practical industrial application.