Highly Selective Separation of Benzene/Cyclohexane by Three-Dimensional Covalent Organic Framework with 8,8-Connected bcu Net Topology

Here, we report the discovery of the first (8,8)-connected three-dimensional (3D) covalent organic framework (COF), TUS-88, having bcu topology by linking an 8-connected D4h-symmetric quadrangular prism node to an 8-connected D2h-symmetric tetragonal prism node. Derived from the π-aromatic conjugated system of pyrene and the abundant aromatic phenyl rings composing the COF scaffold, which promotes stronger π···π interactions with aromatic benzene (Bz) molecules, a superlative Bz uptake of 464 cm3 g–1 was achieved for TUS-88, coupled with exemplary cyclohexane (Cy) uptake of 224 cm3 g–1 and ideal Bz/Cy selectivity of 2.07 which are the current benchmark. Breakthrough experiments accomplished using a Bz/Cy (1:1, v/v) mixture corroborated the preferential adsorption of Bz by the COF from the mixture to generate high-purity Cy with a significant time interval of 75.4 min g–1 and a record-setting Bz/Cy breakthrough selectivity of 2.46.