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.