Fluorinated Squareimines for Molecular Sieving of Aromatic over Aliphatic Compounds

Abstract

The development of more energy‐efficient separation technologies is essential. Especially the separation of cyclic aliphatic hydrocarbons from their aromatic counterparts remains a significant challenge due to azeotrope formation and similar physical properties, often requiring energy‐intensive processes. Herein, we introduce a novel class of electron‐deficient macrocycles with a unique rectangular structure to optimise π···π interactions within the pore, enabling the highly selective molecular sieving of aromatic compounds from mixtures. Utilising dynamic covalent imine chemistry, the squareimine NDI2F42‐based crystalline functional material is directly obtained from the reaction mixture in a single self‐assembly step in high yields of 84%, alongside the larger NDI2F82 congener, which can be obtained in 69% yield. In vapour sorption and diffusion experiments, NDI2F42 demonstrates rapid adsorption kinetics with selectivities of 97:3 for benzene over cyclohexane and 93:7 for toluene over methylcyclohexane, while single‐crystal and powder X‐ray diffraction studies confirm that the selectivity is primarily governed by directed π···π interactions.