Simultaneously enhanced gas permeability, selectivity and aging stability of carbon molecular sieve membranes by the molecule doping of silicon

Simultaneously enhancing the gas permeability , selectivity and aging stability of carbon molecular sieve membrane (CMSM) is extremely difficult. Facing such poser, a novel silicon doped CMSM at molecular level was prepared by copolymerizing siloxane with single Si– O –Si unit into the backbone of polyimide (PI). This can effectively avoid prior separated structure or multiple Si– O –Si structures and strongly alter the chains packing and thermostability of PI, finally determine the pore structure and thermodynamic behavior . The simple design adjustment simultaneously exhibits the triple enhanced effects on the gas permeability, selectivity and aging stability. The best molecule doped CMSM exhibits the ultra-high H 2 permeability (12482 Barrer, 87% higher), 26% higher H 2 /CH 4 selectivity, and 32% higher H 2 /N 2 selectivity than pure PI based CMSM. Additionally, such CMSM also has a much better aging stability than pure CMSM and most reported CMSMs . After stabilization, it still maintains a high H 2 permeability (8000 Barrer). And the hyper-aging CMSM also exhibits a good aging resistance showing a H 2 permeability of 5300 Barrer, as well as high selectivity of H 2 /CH 4 (125) and H 2 /N 2 (106) after 35 days. This work opens a new way on designing CMSM with excellent performance through heteroatom doping to need future application.