Breathing‐Assisted Selective Adsorption of C8 Alkyl Aromatics in Zn‐Based Metal‐Organic Frameworks

• Published in: Chemistry : a European journal Vol. 27; no. 60; pp. 14851 - 14857
• Main Authors: Lee, Jihyun, Kim, Younghoon, Son, Younghu, Kim, Hyehyun, Nam Choi, Yong, D'Alessandro, Deanna, Chandra Rao, Purna, Yoon, Minyoung
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 25.10.2021
• Subjects: adsorption; Aromatic compounds; Benzene; Binary mixtures; Boiling points; breathing effect; Chemical separation; Chemistry; Dimethylformamide; Ethane; Ethylbenzene; flexibility; Industrial applications; isomer separation; Isomers; Metal-organic frameworks; Molecular structure; Organic solvents; Pore size; Selective adsorption; Sorption; Water vapor; Xylene; Zinc
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202102640

The breathing phenomenon in metal‐organic frameworks (MOFs) has revealed supramolecular host‐guest interactions that could be beneficial for chemical separation in numerous industrial applications. The cost‐effective purification of C8 alkyl aromatics such as o‐xylene, m‐xylene, p‐xylene, and ethylbenzene remains challenging owing to their similar molecular structures, boiling points, kinetic diameters, polarities, etc. Herein, we report two Zn‐based pillar‐bilayered MOFs, denoted [Zn2(aip)2(pillar)] (aip=5‐aminoisophthalic acid; pillar: bpy=4,4’‐bipyridine or bpe=1,2‐bis(4‐pyridyl)ethane) that exhibit a breathing effect depending on the adsorbed guest molecules. Guest‐dependent sorption studies in organic solvents such as N,N‐dimethylformamide, methanol, benzene, and water vapor display reversible structural flexibility through the breathing effect in both framework compounds. The experiments conducted on C8‐alkyl aromatics resulting in both MOF compounds can access these isomers in the shrunken pores, and thereby expand the pore size by framework breathing. In C8 binary mixtures, these Zn‐MOFs exhibit selective sorption properties based on the different interactions between guest C8 aromatics and the framework structure. Breathing exercises: Two Zn‐based metal‐organic frameworks showed reversible structural flexibility through the breathing phenomenon upon the addition and removal of guest molecules. Moreover, these two MOF compounds demonstrated selective sorption of C8 alkyl aromatics in their binary mixtures.