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

Abstract

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.

Dative B←N bonds based crystalline organic framework with permanent porosity for acetylene storage and separation

“…For the C 2 H 2 molecule, two H atoms form four C–H⋯C hydrogen bonds with the C atoms of four pyridine rings (∼2.83 Å), as reported in other MOF materials. 67 These similar weak interactions explain the small difference in Q st between C 2 H 2 and CO 2 , but as the hydrogen bonds formed by the framework with C 2 H 2 are shorter than CO 2 , it leads to stronger interactions for C 2 H 2 from the framework.…”

“…The adsorbed CO2 molecule shows a sideon orientation while C2H2 has an end-on orientation in terms of the local pore environment, which has also been observed in previous reports to reduce energy. 66 67 These similar weak interactions explain the small difference in Qst between C2H2 and CO2, but since the hydrogen bonds formed by the framework with C2H2 are shorter than CO2, it leads to stronger interactions for C2H2 from the framework.…”

Potential of a pH-Stable Microporous MOF for C2H2/C2H4 and C2H2/CO2 Gas Separations under Ambient Conditions

“…On the other hand, at 295 K, for C 2 H 2 /C 2 H 4 , the selectivity value was 3.39 (1:99) and 4.61 (50:50) (Figure b,d). These C 2 H 2 /C 2 H 4 selectivity values at 295 K were higher and/or comparable to those of PAF - 110 (3.9–8.0; 50:50); NUM-11 (3.0, 50:50); CTF-PO71 (2.8; 50:50); Fe-MOF-74 , (1.87; 50:50); M′MOF-2a (1.93; 50:50); NOTT-300 (2.3; 50:50); and ZJNU-14 (1.59; 1:99 at 298 K) but lower than those of SIFSIX-2-Cu-I (41.01; 50:50) and UTSA-300a (>10 4 ; 50:50) as depicted in Figure f.…”

Substituent Engineering-Enabled Structural Rigidification and Performance Improvement for C2/CO2 Separation in Three Isoreticular Coordination Frameworks

“…In particular, at 298 K and 109 kPa, the C 2 H 2 /CO 2 (1/1, v/v) adsorption selectivities were predicted to be 4.66, 3.82, and 2.78 for ZJNU-132 , ZJNU-131 , and ZJNU-130 , respectively. The selectivity value of ZJNU-132 is lower than that of the several top-performing MOFs such as NCU-100 (1787), UTSA-300 (743), and CPL-1-NH 2 (119), but higher than that of some literature compounds such as FJU-90 (4.3), CAU-10-H (4.0), FUT-1 (4.0), [Ni­(NH 2 -BPTC) 0.5 ] (3.5), NUM-11 (3.0), JXNU-14 (2.97), UPC-200­(Fe)-F-BIM (2.94), SNNU-27-Fe (2.0), and [Ca­(dtztp) 0.5 ] (1.7) . Considering that the adsorption selectivity and uptake capacity jointly dictated the separation efficiency, Krishna proposed a new index for direct comparison of the separation performance, which was termed the separation potential Δ q taking the above two metrics into account .…”