Removal of Trace Benzene\nfrom Cyclohexane Using a\nMOF Molecular Sieve

Cyclohexane\n(Cy), commonly produced by the catalytic\nhydrogenation\nof benzene (Bz), is used in large quantities as a solvent or feedstock\nfor nylon polymers. Removing trace unreacted Bz from the Cy product\nis technically difficult due to their similar molecular structures\nand physical properties. Herein, we report that a metal–organic\nframework (MOF) adsorbent shows a molecular sieving effect for Bz\nand Cy with record-high Bz/Cy adsorption selectivities (216, 723,\nand 1027) in their liquid mixtures (v/v = 1:1, 1:10, and 1:20), and\ntraps Bz molecules effectively even at low partial pressure in the\nvapor phase (e.g., 2.49 mmol/g at 8.2 Pa) or at low content in liquid-phase\nCy (e.g., 128 mg/g at 20 ppm). Over 99% removal of trace Bz (1000\nppm) from liquid Cy could be achieved in one simple stripping step\nat room temperature using this sorbent, producing a Cy with >99.999%\npurity. Single-crystal structure analyses for guest-free and Bz-loaded\nphases of the MOF disclosed that a narrow slit-like pore aperture\nand the strong uniting of multiple weak host–guest and guest–guest\ninteractions are the co-origin of its distinct adsorption property\nfor Bz and Cy.