Precise Kinetic Separation of Hexane Isomers via Morphology Engineering of Metal-Organic Frameworks with Diffusion-Selective Pore Structure.

Abstract

Hexane isomer separation is critical to advancing sustainable and high-value refining in the petrochemical industry. However, precise separation of multi-component hexane mixtures with similar molecular structures remains a bottleneck. Herein, we report a novel metal-organic framework (Cu-3,3-bipyridine-SIFSIX, termed as ZU-621) featuring a tailored diffusion-selective pore structure, synergistically integrated with crystal size engineering, that enables precise and efficient separation of hexane isomers. Owing to the uniquely engineered dumbbell-shaped, misaligned electronegative pore environment, ZU-621 exhibits intrinsic kinetic discrimination among hexane isomers based on the alkyl spatial distribution. Complementary crystal morphology engineering further fine-tunes the adsorption-diffusion behavior, affording precise kinetic separation across linear, mono-branched, and di-branched isomer pairs. As a result, this kinetic-morphology synergistic approach achieved benchmark separation performance as evidenced by record gasoline productivity (research octane numbers, RON > 95, 49.8 L kg-1) along with precise, multi-objective separation across five hexane isomers.