Molecular-Sieving Separation of C6 Alkane Isomers by a Scalable Copper-Based MOF with Interconnected 2D Channels

Abstract

The separation of alkane isomers based on their degree of branching is essential for optimizing ethylene feedstocks and for manufacturing high-octane gasoline blends, yet remains challenging because of their nonpolar nature and nearly identical physicochemical characteristics. Herein, we report molecular-sieving separation of C6 alkane isomers by CuHTPO, a copper-based metal–organic framework with an interconnected two-dimensional “contracted window-expanded cavity” pore architecture. Single-component adsorption isotherms show that CuHTPO selectively adsorbs n-hexane (2.31 mmol g–1) and monobranched alkanes, while completely excluding dibranched isomers. Vapor-phase breakthrough experiments further demonstrate its complete exclusion of dibranched alkanes and, notably, kinetic discrimination between the linear and monobranched isomers. CuHTPO can be readily prepared on a gram scale, and its shaped pellets largely preserve the separation capability, as verified by both vapor-phase and liquid-phase breakthrough measurements. Abinitio calculations reveal that the confined pore aperture dictates the size exclusion and kinetic differentiation, thus providing a molecular-level rationale for the observed separation behavior.