Modulator Engineering of a MOF: Minimizing Defects to Boost Molecular-Sieving C₃F₈ Purification

Purification of perfluoropropane (C₃F₈) by molecular sieving is highly desired, but nonideal crystallization and structural defects compromise sieving efficiency. In this study, a formic acid modulation strategy was developed to fabricate MOF-801 with high crystallinity and minimized defects, enabling ideal molecular-sieving C₃F₆/C₃F₈ separation with negligible C₃F₈ co-adsorption. Satisfactorily, the optimized non-defect ND-MOF-801 exhibits strong affinity for C₃F₆ (62.4 cm³ g^-1 at 1 bar) but a record-low C₃F₈ uptake capacity of 0.26 cm³ g^-1 due to rigorous size exclusion, affording an unprecedented C₃F₆/C₃F₈ uptake ratio of 240. Meanwhile, it selectively captures C₂F₆ (48.2 cm³ g^-1) and CF₄ (23.3 cm³ g^-1) over C₃F₈, achieving the first reported sieving separation of the ternary CF₄/C₂F₆/C₃F₈ mixture. Dynamic breakthrough experiments confirm the efficient separation of both binary C₃F₆/C₃F₈ and ternary CF₄/C₂F₆/C₃F₈ mixtures, enabling one-step purification of C₃F₈ with ultra-high purity (>99.999%). Notably, ND-MOF-801 can be easily scaled up to 100 g via a facile reflux method without loss of the superior sieving performance. Collectively, this work not only delivers a practical adsorbent for high‑purity C₃F₈ production, but also highlights formic acid modulation as a versatile approach to engineer defect‑minimized, high‑crystallinity frameworks for ideal molecular sieving.