Sulfur-doped crown ether graphane for enhanced helium separation†
Abstract
Efficient helium (He) separation is essential for its application in high-tech industries, but existing separation membranes often exhibit limited selectivity and efficiency. This study proposes an effective strategy to enhance He separation performance using a sulfur-doped crown ether graphane membrane (CG-S6). Through first-principles calculations, we systematically assessed the separation barriers and selectivity of CG-S6 against five common atmospheric gases (He, Ne, Ar, N2, and CH4). The results show that CG-S6 retains excellent thermodynamic stability and features a reduced band gap of 2.73 eV, a 29% decrease compared to the original CG-6, primarily due to the electronic contributions of sulfur atoms near the Fermi level. Optically, CG-S6 exhibits enhanced ultraviolet absorption with a broader range and a notable redshift compared to CG-6. Importantly, CG-S6 demonstrates a He separation barrier of 0.20 eV, significantly lower than those for Ne (0.50 eV), Ar (1.97 eV), N2 (1.52 eV), and CH4 (3.12 eV). Remarkably, the selectivity of He over the other gases ranges from 331.15 to 1 × 1020 across the temperature range of 0–600 K, effectively overcoming the selectivity limitations of the original CG-6 membrane and outperforming several established porous materials. These results suggest that CG-S6 is a promising candidate for He separation. Moreover, sulfur doping proves to be an effective strategy for tuning the separation properties of membrane materials, providing a new theoretical perspective for the development of high-performance He-selective membranes.