Electronic-Structure-Directed Pore Engineering in Metal-Organic Frameworks for Molecular Sieving of C3F6/C3F8.

Trace removal of hexafluoropropylene (C3F6) from octafluoropropane (C3F8) 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 C3F6/C3F8 separation, in which Jahn-Teller-active Cu2+ directs framework reconstruction from the large-aperture channels of ZnTPO (H3TPO = 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 C3F8 with productivities of 314.9 and 2819 L kg-1 from 1/9 and 1/99 C3F6/C3F8 mixtures, respectively. Optical imaging at the single-particle level directly visualizes the rapid transport of C3F6 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.