Source: School of Chemistry
Written by: School of Chemistry
Edited by: Tan Rongyu, Wang Dongmei

Butane (n-C4H10) and pure isobutane (i-C4H10) have widespread applications. However, the separation of butane isomers is energy consuming. Adsorptive separation based on porous materials may replace the energy-intensive distillation technology. Among many adsorptive separation mechanisms, molecular sieving is simple and effective, but it is still extremely difficult to precisely control the pore size. Framework flexibility may be a new strategy to realize molecular sieving, but its effect and mechanism are still controversial. On the other hand, strong bonds with high directionality, such as covalent and coordination bonds, are essential for maintaining permanent porosity. By contrast, molecular crystals based on hydrogen bonds or weak interactions, suffering from the lack of structural rigidity and designability, rarely show porosity and have not been used for adsorptive separation.

Recently, professor Jie-Peng Zhang’s group from School of Chemistry, Sun Yat-sen University, synthesized a hydrogen-bonded porous molecular crystal. The material exhibits high chemical stability in water at pH 2‒13 and exceptional hydrophobicity with a water contact angle of 134o. More important, single-component butane and isobutane adsorption showed ideal butane/isobutane molecular sieving. But quantitative column breakthrough experiments showed that, regardless of a high adsorption selectivity of 23, trace amount of isobutane was co-adsorbed during butane adsorption. Computational simulations and in situ single-crystal/powder X-ray diffraction revealed slight pore size changes during adsorption/desorption, which is the key of co-adsorption.

This work is recently published on Angewandte Chemie International Edition. Chun-Ting He (Jiangxi Normal University) and Jie-Peng Zhang (Sun Yat-sen University) are the corresponding authors and the first author is PhD candidate Zi-Ming Ye (Sun Yat-sen University). This work was supported by the National Natural Science Foundation of China (21731007, 21821003, and 21901089) and the Guangdong Pearl River Talents Program (2017BT01C161). C.-T. H. acknowledges the support of “Young Elite Scientists Sponsorship Program” by CAST.

Link to the paper: https://onlinelibrary.wiley.com/doi/abs/10.1002/ange.202011300