Inversed Benzene/Cyclohexene/Cyclohexane Adsorption Selectivities for One-Step Purification of Cyclohexene and Beyond

Abstract

Separation of benzene/cyclohexene/cyclohexane (Bz/Cye/Cya) mixtures, especially purification of Cye, is crucial but challenging in the petrochemical industry. Here, we report two new metal–organic frameworks with opposite adsorption selectivities for on-demand separation/purification of Bz/Cye/Cya mixtures. Although they possess similar frameworks and pore structures, their pore surfaces are functionalized by hydrophobic ethyl and hydrophilic hydroxymethyl groups, which interact conversely with Bz/Cye/Cya, giving a record-high Bz selectivity (129) and the first example of Cya/Cye/Bz selectivity (18.6), respectively. Equimolar ternary mixture breakthrough experiments showed that they could directly produce high-purity Cya (99.5%+, 0.39 mmol g^–1) or Bz (99.5%+, 0.25 mmol g^–1), and the tandem connection of two adsorbents enabled direct production of high-purity Cye (99.5%+, 0.37 mmol g^–1) in a one-step adsorption process. Further, a bypass-tandem strategy is proposed to not only greatly improve Cye productivity (99.5%+, 0.57 mmol g^–1) but also simultaneously produce high-purity Cya (99.5%+, 0.36 mmol g^–1).