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

Abstract 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.