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 CO2 as the primary byproduct alongside H2O and CH4, 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 H2 purification. Pore size is precisely tuned at the picometer scale (< 1 Å) by altering the anion linkers (SiF6 2-, GeF6 2- and TiF6 2-), enabling efficient H2 purification through the synergy between subtle window adjustments and F-site-enhanced CO2 affinity. The SIFHBF-Cu membrane combines the optimal size-exclusion and strongest HBF-CO2 interactions, exhibiting excellent H2/CO2 selectivity (501) and ternary gas separation (H2/CO2: 477, H2/CH4: 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.