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

Abstract

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.