Efficient separation of xylene isomers by a guest-responsive metal-organic framework with rotational anionic sites

Xili Cui; Zheng Niu; Chuan Shan; Lifeng Yang; Jianbo Hu; Qingju Wang; Pui Ching Lan; Yijian Li; Lukasz Wojtas; Shengqian Ma; Huabin Xing

doi:10.1038/s41467-020-19209-7

Efficient separation of xylene isomers by a guest-responsive metal-organic framework with rotational anionic sites

Nat Commun. 2020 Oct 28;11(1):5456. doi: 10.1038/s41467-020-19209-7.

Authors

Xili Cui¹, Zheng Niu², Chuan Shan³, Lifeng Yang⁴, Jianbo Hu⁴, Qingju Wang⁴, Pui Ching Lan⁵, Yijian Li⁴, Lukasz Wojtas³, Shengqian Ma^{6

7}, Huabin Xing⁸

Affiliations

¹ Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China. cuixl@zju.edu.cn.
² College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China.
³ Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida, 33620, USA.
⁴ Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.
⁵ Department of Chemistry, University of North Texas, 1508W Mulberry Street, Denton, Texas, 76201, USA.
⁶ Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida, 33620, USA. Shengqian.Ma@unt.edu.
⁷ Department of Chemistry, University of North Texas, 1508W Mulberry Street, Denton, Texas, 76201, USA. Shengqian.Ma@unt.edu.
⁸ Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China. xinghb@zju.edu.cn.

Abstract

The separation of xylene isomers (para-, meta-, orth-) remains a great challenge in the petrochemical industry due to their similar molecular structure and physical properties. Porous materials with sensitive nanospace and selective binding sites for discriminating the subtle structural difference of isomers are urgently needed. Here, we demonstrate the adaptively molecular discrimination of xylene isomers by employing a NbOF₅^2--pillared metal-organic framework (NbOFFIVE-bpy-Ni, also referred to as ZU-61) with rotational anionic sites. Single crystal X-ray diffraction studies indicate that ZU-61 with guest-responsive nanospace/sites can adapt the shape of specific isomers through geometric deformation and/or the rotation of fluorine atoms in anionic sites, thereby enabling ZU-61 to effectively differentiate xylene isomers through multiple C-H···F interactions. ZU-61 exhibited both high meta-xylene uptake capacity (3.4 mmol g^-1) and meta-xylene/para-xylene separation selectivity (2.9, obtained from breakthrough curves), as well as a favorable separation sequence as confirmed by breakthrough experiments: para-xylene elute first with high-purity (≥99.9%), then meta-xylene, and orth-xylene. Such a remarkable performance of ZU-61 can be attributed to the type anionic binding sites together with its guest-response properties.