Rational design of a polyphenyl octacarboxylate HOF for highly selective separation of benzene over cyclohexane

Abstract

The separation of benzene and cyclohexane is a long-standing challenge in the petrochemical industry, yet conventional distillation remains highly energy-intensive due to the nearly identical boiling points of the two molecules. Adsorptive separation offers a far more energy-efficient alternative; however, the development of adsorbents that simultaneously combine stable lightweight structures, high adsorption capacity, and strong selectivity remains difficult. To overcome these limitations, we present a robust hydrogen-bonded organic framework, H₈ETTOB-HOF, constructed from a polyphenyl octacarboxylic acid linker. Its precisely engineered pore architecture and tailored electrostatic environment work synergistically to enhance benzene affinity, affording exceptional benzene/cyclohexane selectivity (16.9) and a high adsorption capacity (3.9 mmol g⁻¹ at 298 K, 13 kPa), surpassing all previously reported HOFs. Density functional theory shows that the synergistic C–H⋯O and C–H⋯π interactions facilitate benzene capture. Experimental investigations employing dynamic columns demonstrate efficient one-step benzene purification from equimolar mixtures, showcasing excellent recyclability. This work highlights a strategic approach to constructing stable, multifunctional HOFs for challenging hydrocarbon separations.