Separation and Purification of Xylene by Self-Assembly of a Tunable N → B Adduct
Xiaofan Wang, Zhijun Ke, Lizhen Liu, Jie Huang, Yisi Yang, Wen Dai, Chulong Liu, Zhangjing Zhang, Zizhu Yao, Shengchang Xiang
Abstract
It is challenging to obtain isomers in a pure form because of the similarities in their physicochemical properties. meta-Xylene (MX) accounts for the largest proportion of commercial xylene, which is difficult to separate from xylene through low-temperature crystallization and fractionation or adsorbents. In this work, the synthesis of the N → B adduct with preferential selectivity to meta-xylene is obtained by the combination of 1,4-bis(benzodioxaborole)benzene and 1,2-di(4-pyridyl)ethylene in a molar ratio of 1:1. The high selectivity to MX of the N → B adduct may be mainly attributed to the lower energy of the trans-structure of the two catecholate groups. Also, the forces between the guest and the host molecule influence the selectivity. In the liquid xylene mixture, the selective order of the N → B adduct is meta-xylene > ortho-xylene > para-xylene. And the N → B adduct can be reused without losing capture capacity.