Hybrid carbon molecular sieve membranes having ordered Fe3O4@ZIF-8-derived microporous structure for gas separation

Carbon molecular sieve (CMS) membranes have great promise in CO 2 capture. However, tortuous transport passageways restrict the enhancement in the permeability due to the presence of disordered porous structure and dead-end pore. Herein, the growth of ZIF-8 layer on the surface of Fe 3 O 4 formed magnetic core-shell Fe 3 O 4 @ZIF-8 particles, which were fixed into 6FDA/ODA:DABA polyimides under magnetic field-induction to fabricate a precursor membrane with vertically oriented chain-like particles. It was then pyrolyzed to form hybrid carbon molecular sieve (HCMS) membranes with ordered microporous structure under high temperature conditions. The cross-section scanning electron microscopy images and N 2 adsorption for resultant HCMS membranes indicate that Fe 3 O 4 @ZIF-8-derived carbons frameworks were vertically oriented to form the ordered microporous structure, which also had good compatibility with carbon matrix stemmed from 6FDA/ODA:DABA polyimides. The as-prepared HCMS membranes embedded with 5 wt% Fe 3 O 4 @ZIF-8 manifested a highest gas separation performance (permeability of 5130 Barrer; CO 2 /N 2 selectivity of 29; CO 2 /CH 4 selectivity of 48), outperforming the pristine CMS membranes, which were near and beyond 2019 CO 2 /N 2 and CO 2 /CH 4 upper bounds, separately. These good separation performances resulted from vertical chain-like microporous particles, which provided fast transport channels to accelerate CO 2 diffusion rate. In addition, we supposed that Fe 3 O 4 prevent ZIF-8 frameworks from destruction during the pyrolysis and promote the size screening capability. More importantly, this membrane exhibited excellent aging resistance over 30 days aging testing compared to pristine CMS membranes. Therefore, it affords a feasible way for carbon capture from flue gas and natural gas.