Ultra-Microporous Anion-Pillared Metal-Organic Framework with Fast Adsorption Kinetics for C3H6/C3H8 Separation

Separating a propylene/propane (C3H6/C3H8) mixture is essential in the chemical industry for producing polymer-grade propylene. Emerging adsorbent-based separation methods are an energy-efficient alternative, particularly molecular sieving, offering excellent selectivity and purity by excluding undesired gases. However, precise pore structure and adsorption sites are required for achieving complete exclusion, posing a daunting synthetic challenge. Here, we demonstrate sieving separation of C3H6/C3H8 mixtures using the customized ultra-microporous anion-pillared MOF, TaOFFIVE-1-Ni (1 = pyrazine) via precise control of aperture size and binding sites. The dynamic, narrow pore window allows for the selective passage of C3H6, exhibiting excellent C3H6 uptake of 72.7 cm3 cm-3 with rapid adsorption kinetics while blocking slightly larger C3H8 (5.9 cm3 cm-3) under ambient conditions. Computational simulations revealed that electronegative fluorine sites provide strong binding interactions, thereby enhancing adsorption capacity. Dynamic breakthrough experiments further confirm the excellent potential of TaOFFIVE-1-Ni, delivering high-purity propylene (≥95.5%) from binary propylene/propane mixtures. Additionally, the high thermal stability, stability in aqueous acidic and basic media, and g-scale synthesizability of this MOF make it well-suited for long-term use in industrial propylene purification.