Comprehensive Pore Tuning in an Ultrastable Fluorinated Anion Cross-Linked Cage-Like MOF for Simultaneous Benchmark Propyne Recovery and Propylene Purification

Propyne/propylene (C₃H₄/C₃H₆) separation is an important but challenging industrial process to produce polymer-grade C₃H₆ and recover high-purity C3H4. Herein, we report an ultrastable TiF₆²⁻ anion cross-linked metal–organic framework (ZNU-2) with precisely controlled pore size, shape and functionality for benchmark C₃H₄ storage (3.9/7.7 mmol g⁻¹ at 0.01/1.0 bar and 298 K) and record high C₃H₄/C₃H₆ (10/90) separation potential (31.0 mol kg⁻¹). The remarkable C₃H₄/C₃H₆ (1/99, 10/90, 50/50) separation performance was fully demonstrated by simulated and experimental breakthroughs under various conditions with excellent recyclability and high productivity (42 mol kg⁻¹) of polymer-grade C₃H₆ from a 1/99 C₃H₄/C₃H₆ mixture. A modelling study revealed that the symmetrical spatial distribution of six TiF₆²⁻ on the icosahedral cage surface provides two distinct binding sites for C₃H₄ adsorption: one serves as a tailored single C₃H₄ molecule trap and the other boosts C₃H₄ accommodation by cooperative host–guest and guest–guest interactions.