Anion-pillared porous materials with suitable pore size for the efficient discrimination of cyclohexene from cyclohexane

The separation of medium and high carbon number linear and cyclic olefins and alkanes is a great challenge in the petrochemical industry, due to the closer molecular structure and physical properties with increased carbon chains. The adsorptive separation offers an alternative to conventional energy-intensive distillations, but its separation efficiency is limited by the low adsorption capacity and high energy penalty for regeneration. Herein, we employed anion-pillared porous materials (SIFSIX-1-Cu, SIFSIX-2-Cu-I, and ZU-61) that addressed the separation challenge of cyclohexene and cyclohexane. ZU-61 with suitable pore size and high-density anions exhibits excellent cyclohexene uptake capacity (6.11 mmol·g−1), 3 times the common zeolite 13X (2.11 mmol·g−1) as well as the high separation selectivity. Combined with single-crystal diffraction experiment and simulation studies, the results demonstrate the dominant role of anions in discriminating different kinds of H atoms (CH and CH), which enables the efficient discrimination towards cyclohexene from cyclohexane. Moreover, benefiting from the moderate strength enabled by the anions, the cyclohexene saturated ZU-61 could be easily regenerated under 80 °C, the value is lower than that of zeolite 13X (200 °C). This work demonstrates the superiority of anions in recognizing the olefins and paraffins with medium and high carbon number and offers guidance to the related challenging separations.