Efficient C₂H₂ Separation from CO₂ and CH₄ within a Microporous Metal–Organic Framework of Multiple Functionalities

Abstract

The separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) and methane (CH 4 ) is of great significance, but remains challenging, because of their similar physicochemical properties, and it currently has received substantial research interest by using adsorptive separation based on metal−organic frameworks (MOFs). Herein, a new microporous Cu-MOF, [Cu(5-OH-IPA 2− )-(DPYA)(H 2 O)] (BUT-318, where 5-OH-IPA 2− = 5-hydroxyisophthalate and DPYA = 4,4′-dipyridylamine) has been synthesized successfully under solvothermal conditions, which exhibits excellent separation performance for C 2 H 2 /CO 2 and C 2 H 2 /CH 4 gas mixtures. The presence of Cu(II) open metal sites and different Lewis base sites (−OH and −NH) make the activated BUT-318 efficiently bind C 2 H 2 and exhibit high adsorption capacity under low pressure (24.52 and 9.1 cm 3 g −1 under 0.01 bar, at 273 and 298 K, respectively). The corresponding IAST (ideal adsorbed solution theory) selectivity was 9.8 and 244.3 at 273 K and 1 bar for an equimolar C 2 H 2 /CO 2 and C 2 H 2 /CH 4 mixture. The separation performance and reusability under dynamic conditions were also confirmed by column breakthrough experiments, making BUT-318a a promising candidate for the practical C 2 H 2 separation.

Ligand Conformation Fixation Strategy for Expanding the Structural Diversity of Copper-Tricarboxylate Frameworks and C2H2 Purification Performance Studies

“…In particular, ZJNU-133 displayed higher adsorbing capacities toward C 2 H 2 than CO 2 and CH 4 . The molar ratios of C 2 H 2 /CO 2 and C 2 H 2 /CH 4 at the normal pressure amount to 1.30 and 3.22 at 298 K, 1.22 and 2.91 at 288 K, and 1.14 and 2.63 at 278 K. The C 2 H 2 /CO 2 molar ratio of 1.30 is comparable to and even surpasses those of some reported coordination framework materials under similar conditions such as TIFSIX-2-Cu-i (0.95), ZJNU-8 (1.11), BUT-318 (1.16), Ca­(dtztp) 0.5 (1.17), PCM-48 (1.17), NKMOF-1-Ni (1.19), MUF-17 (1.2), JNU-1 (1.24), and ATC-Cu (1.25) but is inferior to those of some known MOFs such as UTSA-300 (18.6), and dps-VCo-BDC (1.89) . Apart from different uptake capacities, ZJNU-133 also exhibited higher affinity toward C 2 H 2 than CO 2 and CH 4 , as reflected by the steeper isotherm of C 2 H 2 than CO 2 and CH 4 at the low-pressure region.…”