Green Kilogram-Scale MOF Synthesis and Acetone-Induced Structural Evolution for Sieving Benzene from Cyclohexane

The separation of benzene/cyclohexane represents a crucial yet challenging process in the petrochemical industry, as their azeotropic mixture cannot be effectively separated through simple distillation. Herein, we report a facile kilogram-batch synthesis of a metal-organic framework (JNU-81-A) in a water/ethanol solution at room temperature. When wetted by acetone, JNU-81-A undergoes a single-crystal-to-single-crystal structural evolution, yielding JNU-81-B with altered coordination environments. Interestingly, further structural evolution was observed upon removal of acetone, resulting in JNU-81-C with one-dimensional channels in the a-axis direction. JNU-81-C exhibits benzene-induced gate-opening flexibility, enabling a sieving effect of benzene from cyclohexane. Liquid-phase column breakthrough experiments demonstrate the ability of JNU-81-C to collect ultrahigh-purity (99.9%) cyclohexane from benzene/cyclohexane mixtures. Moreover, liquid-phase extraction experiments were carried out at a 1000 mL scale using the fabricated JNU-81-C pellets, allowing for increasing the cyclohexane purity from 95% to 99.5% with an average recovery rate of 95% for ten cycles. This work presents an energy-efficient adsorption-based separation of benzene/cyclohexane mixtures, providing an alternative approach for this challenging industrial process.