A Hydrogen‐Bonded yet Hydrophobic Porous Molecular Crystal for Molecular‐Sieving‐like Separation of Butane and Isobutane

• Published in: Angewandte Chemie International Edition Vol. 59; no. 51; pp. 23322 - 23328
• Main Authors: Ye, Zi‐Ming, Zhang, Xue‐Wen, Liao, Pei‐Qin, Xie, Yi, Xu, Yan‐Tong, Zhang, Xue‐Feng, Wang, Chao, Liu, De‐Xuan, Huang, Ning‐Yu, Qiu, Ze‐Hao, Zhou, Dong‐Dong, He, Chun‐Ting, Zhang, Jie‐Peng
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 14.12.2020
• Edition: International ed. in English
• Subjects: Adsorbents; Adsorption; adsorptive separation; Adsorptivity; Bonding strength; Butane; Computer applications; Contact angle; Crystal structure; Crystals; Hydrogen; Hydrogen bonding; Hydrogen bonds; hydrogen-bonded organic frameworks (HOFs); Hydrophobicity; molecular sieve; Selectivity; Separation; single-crystal-to-single-crystal
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202011300

Porous molecular crystals sustained by hydrogen bonds and/or weaker connections are an intriguing type of adsorbents, but they rarely demonstrate efficient adsorptive separation because of poor structural robustness and tailorability. Herein, we report a porous molecular crystal based on hydrogen‐bonded cyclic dinuclear AgI complex, which exhibits exceptional hydrophobicity with a water contact angle of 134°, and high chemical stability in water at pH 2–13. The seemingly rigid adsorbent shows a pore‐opening or nonporous‐to‐porous type butane adsorption isotherm and complete exclusion of isobutane, indicating potential molecular sieving. Quantitative column breakthrough experiments show slight co‐adsorption of isobutane with an experimental butane/isobutane selectivity of 23, and isobutane can be purified more efficiently than for butane. In situ powder/single‐crystal X‐ray diffraction and computational simulations reveal that a trivial guest‐induced structural transformation plays a critical role. A rigid hydrogen‐bonded porous molecular crystal shows not only exceptionally high hydrophobicity and chemical stability, but also molecular‐sieving‐like separation of butane/isobutane associated with a trivial guest‐induced structural transformation revealed by powder/single‐crystal X‐ray diffraction and computational simulations.