Introducing halogen-bonded gates in zeolitic frameworks for efficient benzene/cyclohexene/cyclohexane separation

Abstract

The separation of C₆ cyclic hydrocarbons (benzene, cyclohexene, and cyclohexane) is one of the most challenging chemical separations in the petrochemical industries. Herein, we design and synthesize a new SOD-topology metal azolate framework (MAF) with aperture gating behaviour controlled by C‒Br‧‧‧N halogen bonds, which exhibits distinct temperature- and guest-dependent adsorption behaviours for benzene/cyclohexene/cyclohexane. More importantly, the MAF enables the efficient purification of benzene from its binary and ternary mixtures (selectivity up to 113±2; purity up to 98%+), which is the highest record for benzene/cyclohexane/cyclohexene separation to date. Single-crystal diffraction analyses and computational simulations revealed that halogen bonds play a critical role in the gating and diffusion process, which is the first example of halogen-bonding controlled gating for highly effective adsorptive separation.