Polyimide-derived carbon molecular sieve membranes for high-efficient hydrogen purification: The development of a novel phthalide-containing polyimide precursor

Hydrogen-based economy has been considered as a potential solution for energy security and sustainability in the future. And the ever-increasing demand for high-purity hydrogen (H-2) provides an urgent force for the H-2 purification technologies. Herein, a novel polyimide (BATPPP-6FDA) with rigid and contorted structure was synthesized and used as a precursor to fabricate the carbon molecular sieve membranes (CMSMs) for H-2 purification. The structural changes from precursor to CMS were detected and the H-2 separation performance of the membranes was optimized by the pyrolysis temperature. The CMSM pyrolyzed at 550 degrees C exhibited the highest H-2 permeability of 10054.1 Barrer and moderate H-2 permselectivity due to its highly disordered and turbostratic carbon structure originated from the generally decomposition of thermally labile -CF3 groups and the lactone rings of phthalide structure in the early stages (<550 degrees C) of pyrolysis. As the pyrolysis temperature raised, the H(2 )permeability of the derived CMSM decreased, and the H-2 permselectivity enhanced greatly. The CMSM pyrolyzed at 800 degrees C demonstrated a high H-2 permeability of 2622.4 Barrer and superior selectivity with H-2/N-2 of 524.48, H-2/CH4 of 1248.76 and H-2/CO2 of 7.51, respectively, which was attributed to the low densification of carbon structure resulting from the rigid and contorted structure of the BATPPP-6FDA precursor. The excellent H-2 separation performance showed a great potential in hydrogen purification application.

Automated summary

The hydrogen-based economy is considered a potential solution for energy security and sustainability in the future. The demand for high-purity hydrogen has led to the development of hydrogen purification technologies. A novel polyimide was synthesized and used for fabricating carbon molecular sieve membranes (CMSMs) for hydrogen purification. The pyrolysis temperature was optimized to enhance the H-2 separation performance of the membranes.