A B←N framework based on 1D dative B←N polymers for exclusive recognition and separation of benzene from its azeotrope

Separating benzene from its cyclohexane and cyclohexene mixtures is a challenge in the petrochemical industry. Herein, we developed a B←N framework (BNF) approach, for the first time, to realize a BNF-2 for highly selective recognition and separation of benzene. Although the primary moieties of BNF-2 are one-dimensional (ID) B←N polymers, in the presence of benzene, such chains can be self-assembled into a two-dimensional (2D) framework of open structure to encapsulate benzene molecules; therefore, BNF-2 can be readily utilized for separating benzene from its liquid binary C₆H₆/C₆H₁₂ (1:1) and C₆H₆/C₆H₁₀ (1:1) and ternary C₆H₆/C₆H₁₀/C₆H₁₂ (2:1:1) mixtures to obtain benzene with purity of 99.2%, 97.8%, and 97.2%, respectively. Importantly, the included benzene molecules can be released simply by gentle heating to produce benzene of almost 100% purity, whereas the resulting closed framework material can be straightforwardly recovered and reused through simple recrystallization. Molecular modeling demonstrated the suitable pores in BNF-2 with matchable steric electrostatic potential (ESP) toward C₆H₆.