Electronic‐Structure‐Directed Pore Engineering in Metal–Organic Frameworks for Molecular Sieving of C ₃ F ₆ /C ₃ F ₈

Trace removal of hexafluoropropylene (C 3 F 6 ) from octafluoropropane (C 3 F 8 ) is crucial for producing high‐purity fluorinated electronic gases, yet it remains highly challenging because of their similar molecular dimensions. Here, we report an electronically driven pore‐engineering strategy for C 3 F 6 /C 3 F 8 separation, in which Jahn–Teller‐active Cu 2+ directs framework reconstruction from the large‐aperture channels of ZnTPO (H 3 TPO = tris(4‐carboxyphenyl) phosphine oxide) to the narrow cage‐like pore network of CuHTPO, thereby switching the separation behavior from co‐adsorption to molecular sieving. Consequently, CuHTPO delivers > 99.999% pure C 3 F 8 with productivities of 314.9 and 2819 L kg −1 from 1/9 and 1/99 C 3 F 6 /C 3 F 8 mixtures, respectively. Optical imaging at the single‐particle level directly visualizes the rapid transport of C 3 F 6 through the channels, while single‐crystal X‐ray diffraction, FTIR spectroscopy, and molecular simulations collectively elucidate the structural origin of the electronically regulated sieving behavior. Taken together, this work positions electronic‐structure‐directed pore reconstruction as a powerful material‐design strategy for programming confined pore spaces, enabling robust and recyclable molecular sieving of closely related gases.