Precise Pore Engineering at Picometer Scale on Nanofluidic Membrane for Efficient Hydrogen Purification

Hydrogen, a carbon‐free energy carrier is mainly produced through methane steam reforming, generating CO 2 as the primary byproduct alongside H 2 O and CH 4 , complicating efficient hydrogen purification. Nanofluidic Hydrogen‐bonded framework (HBF) membranes are promising for gas separation, while methods to precisely tailor pores for enhance performance remain scarce. Herein, a series of HBF membranes (SIFHBF‐Cu, GeFHBF‐Cu and TIFHBF‐Cu) are successfully fabricated for H 2 purification. Pore size is precisely tuned at the picometer scale (< 1 Å) by altering the anion linkers (SiF 6 2− , GeF 6 2− and TiF 6 2− ), enabling efficient H 2 purification through the synergy between subtle window adjustments and F‐site‐enhanced CO 2 affinity. The SIFHBF‐Cu membrane combines the optimal size‐exclusion and strongest HBF‐CO 2 interactions, exhibiting excellent H 2 /CO 2 selectivity (501) and ternary gas separation (H 2 /CO 2 : 477, H 2 /CH 4 : 557), with stable performance under dry/wet conditions. This study provides a strategy for ultra‐precise pore engineering, showing potential for other challenging separations like seawater desalination and isomer separation.