A Highly Stable Interpenetrating Cobalt-Based Metal–Organic Framework for <i>n</i> -Butane/ <i>i</i> -Butane Separation

The isolation of n-butane and iso-butane is of great significance in the petrochemical industry. However, their identical molecular weights and similar properties (n-butane: 272.66 K; iso-butane: 261.34 K) pose significant challenges to conventional separation technologies. Herein, we introduce a microporous cobalt-based metal–organic framework (MOF), termed Co-bpy-bpdc, which exhibits interpenetrating structural constraints that facilitate the effective isolation of n-butane and iso-butane. Adsorption measurements demonstrate that Co-bpy-bpdc delivers an n-butane uptake of 1.67 mmol/g at 298 K. Remarkably, the interpenetrating structure endows it with good low-pressure adsorption performance, thermal stability, and ultrahigh n-butane/iso-butane ideal adsorption solution theory (IAST) selectivity (724.6) while retaining exceptional separation efficiency across multiple adsorption–desorption cycles. Kinetic studies on adsorption and theoretical calculations showed that the linear structure of n-butane enables it to precisely match the MOF pores and form an effective π–π stacking, and its excellent separation performance is attributed to the synergy of thermodynamics and kinetics. The dynamic breakthrough experiments further confirmed the good n-butane/iso-butane separation performance of Co-bpy-bpdc at room temperature. Additionally, stability experiments provide additional evidence that the MOF exhibits no significant attenuation in n-butane adsorption after exposure to the atmosphere for two months. These results collectively highlight its potential in practical separation applications, making Co-bpy-bpdc a promising candidate for advancing industrial n-butane/iso-butane separation processes.