Fine pore engineering in a series of isoreticular metal-organic frameworks for efficient C2H2/CO2 separation

• Published in: Nature communications Vol. 13; no. 1; p. 200
• Main Authors: Wang, Jun, Zhang, Yan, Su, Yun, Liu, Xing, Zhang, Peixin, Lin, Rui-Biao, Chen, Shixia, Deng, Qiang, Zeng, Zheling, Deng, Shuguang, Chen, Banglin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.01.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/299/1013; 639/638/263/915; Acetylene; Binding sites; Carbon dioxide; Copper; Density functional theory; Humanities and Social Sciences; Metal-organic frameworks; multidisciplinary; Performance enhancement; Physical properties; Pore size; Porous materials; Room temperature; Science; Science (multidisciplinary); Selectivity; Separation; Work capacity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-27929-7

The separation of C 2 H 2 /CO 2 is not only industrially important for acetylene purification but also scientifically challenging owing to their high similarities in physical properties and molecular sizes. Ultramicroporous metal-organic frameworks (MOFs) can exhibit a pore confinement effect to differentiate gas molecules of similar size. Herein, we report the fine-tuning of pore sizes in sub-nanometer scale on a series of isoreticular MOFs that can realize highly efficient C 2 H 2 /CO 2 separation. The subtle structural differences lead to remarkable adsorption performances enhancement. Among four MOF analogs, by integrating appropriate pore size and specific binding sites, [Cu(dps) 2 (SiF 6 )] (SIFSIX-dps-Cu, SIFSIX = SiF 6 2- , dps = 4.4’-dipyridylsulfide, also termed as NCU-100) exhibits the highest C 2 H 2 uptake capacity and C 2 H 2 /CO 2 selectivity. At room temperature, the pore space of SIFSIX-dps-Cu significantly inhibits CO 2 molecules but takes up a large amount of C 2 H 2 (4.57 mmol g −1 ), resulting in a high IAST selectivity of 1787 for C 2 H 2 /CO 2 separation. The multiple host-guest interactions for C 2 H 2 in both inter- and intralayer cavities are further revealed by dispersion-corrected density functional theory and grand canonical Monte Carlo simulations. Dynamic breakthrough experiments show a clean C 2 H 2 /CO 2 separation with a high C 2 H 2 working capacity of 2.48 mmol g −1 . The separation of acetylene and carbon dioxide by porous materials requires delicate control over the pore size. Herein, the authors fine-tune the pore size at sub-nanometer scale in a series of isoreticular metal-organic frameworks to control the acetylene/carbon dioxide separation performance; subtle structural differences lead to remarkable performance enhancement.