A Novel kgd-Topological Covalent Organic Framework with Optimum Pore Size for Efficient Benzene/Cyclohexane Separation

Separation of benzene and cyclohexane is essential for obtaining high-purity cyclohexane in the chemical industry and for resource recovery from exhaust gas, but is one of the most challenging separation processes due to their highly similar boiling points and kinetic diameters. Herein, based on the isoreticular contraction strategy, a novel covalent organic framework (i.e., HFPB-TAB-COF) with kgd topological structure and average pore size of 5.70 Å, between the kinetic diameters of benzene (5.60 Å) and cyclohexane (6.10 Å), is synthesized for benzene/cyclohexane separation by pore confinement effect. HFPB-TAB-COF has the highest ideal adsorbed solution theory (IAST) selectivity of 36.0 for benzene/cyclohexane separation, and can produce 0.48 mmol g^-1 cyclohexane with purity of +99% from 50:50 (v:v) benzene/cyclohexane mixture under dynamic condition, higher than reported separation materials. Optimizing the pore size of COFs by isoreticular contraction strategy can trigger the pore confinement effect for better meeting the separation challenge in industry.