A Fluorinated Zinc-based Metal-Organic Framework for Efficient Separation of Butane Isomers via Pore Engineering.

Abstract

Separating n-butane/iso-butane is a challenging and energy-intensive task in the petrochemical industry. There have been only several adsorbents reported for C4 paraffins separation while they are confronted in real-world applications with either poor selectivity or low n-butane uptake capacity. In this study, a fluorinated zinc-based metal-organic framework (MOF), Znpyc-CF₃, derived from Znpyc-CH₃ is developed, which has fluorine-containing functional groups on the pore surface that can enhance the interaction with the linear n-butane. Remarkably, this fluorinated porous material demonstrates both high n-butane uptake (55.5 cm³ g⁻¹) and excellent selectivity (IAST selectivity = 187) at ambient temperature. Multicycle breakthrough experiments confirmed its practical performance for real gas mixtures. Znpyc-CF₃ exhibits outstanding stability, maintaining its structural integrity after repeated sorption cycles and dynamic breakthrough tests under both dry and highly humid conditions. The preferential adsorption mechanism of n-butane is further elucidated through Grand Canonical Monte Carlo (GCMC) simulations and Density Functional Theory (DFT) calculations. Overall, this research presents an efficient and stable adsorbent for the separation of butane isomers.