Simultaneous Recognition and Separation of Organic Isomers Via Cooperative Control of Pore‐Inside and Pore‐Outside Interactions

Abstract

Abstract Despite the desirability of organic isomer recognition and separation, current strategies are expensive and complicated. Here, a simple strategy for simultaneously recognizing and separating organic isomers using pillararene‐based charge‐transfer cocrystals through the cooperative control of pore‐inside and pore‐outside intermolecular interactions is presented. This strategy is illustrated using 1‐bromobutane (1‐BBU), which is often produced as an isomeric mixture with 2‐bromobutane (2‐BBU). According to its structure, perethylated pillar[5]arene (EtP5) and 3,5‐dinitrobenzonitrile (DNB) are strategically chosen as a donor and an acceptor. As a result, their cocrystal exhibited stronger pore‐inside interactions and much weaker pore‐outside interactions with 1‐BBU than with 2‐BBU. Consequently, nearly 100% 1‐BBU selectivity is achieved in two‐component mixtures, even in those containing trace 1‐BBU (1%), whereas free EtP5 only achieved 89.80% selectivity. The preference for linear bromoalkanes is retained in 1‐bromopentane/3‐bromopentane and 1‐bromohexane/2‐bromohexane mixtures, demonstrating the generality of this strategy. Selective adsorption of linear bromoalkanes induced a naked‐eye‐detectable color change from red to white. Moreover, the cocrystal are used over multiple cycles without losing selectivity.

Keywords

• intermolecular interactions
• organic isomer
• pillararenes
• recognition
• separation