Authors: Zeyuan Gao, Yongchao Sun, Lu Bai, Tianyou Li, Jianyu Guan, Fake Sun, Fangxu Fan, Gaohong He, Canghai Ma
Published: 2025-01-22
Source: Full article
AbstractMembrane technology has been explored for separating helium from hydrogen in natural gas reservoirs, a process that remains extremely challenging due to the sub‐Ångstrom size difference between H2 and He molecules. Reverse‐selective H2/He separation membranes offer multiple advantages over conventional helium‐selective membranes, which, however, suffer from low H2/He selectivity. To address this hurdle, a novel approach is proposed to tune the ultra‐micropores of carbon molecular sieves (CMS) membranes through fluorination of the polymer precursor. By incorporating ‐CF3 units into the backbone of Tröger's base polymers, the microporosity of CMS is tailored and reverse‐selective H2/He CMS membranes are deployed with remarkable separation performance, surpassing most reported membranes. These CMS membranes exhibit a H2 permeability of 1505.2 Barrer with a notable H2/He selectivity of 3.8. Barometric sorption tests reveal preferential sorption of H2 over He in the fluorinated CMS membranes, which also demonstrate a significantly higher H2/He diffusion selectivity compared to unfluorinated samples. Material studio calculations indicate that the “slim” hydrogen molecule penetrates ultra‐micropores more readily than the spherical He molecule, thus achieving reverse H2/He selectivity. This design approach offers a promising pathway for developing molecularly sieving membranes to tackle the challenging helium separation from natural gas.