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 (H2) provides an urgent force for the H2 pu-rification technologies. Herein, a novel polyimide (BATPPP-6FDA) with rigid and contorted structure was syn-thesized and used as a precursor to fabricate the carbon molecular sieve membranes (CMSMs) for H2 purification. The structural changes from precursor to CMS were detected and the H2 separation performance of the mem-branes was optimized by the pyrolysis temperature. The CMSM pyrolyzed at 550 degrees C exhibited the highest H2 permeability of 10054.1 Barrer and moderate H2 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 C) of pyrolysis. As the pyrolysis temperature raised, the H2 permeability of the derived CMSM decreased, and the H2 permselectivity enhanced greatly. The CMSM pyrolyzed at 800 degrees C demonstrated a high H2 permeability of 2622.4 Barrer and superior selectivity with H2/N2 of 524.48, H2/CH4 of 1248.76 and H2/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 H2 separation performance showed a great potential in hydrogen purification application.

Automated summary

A novel polyimide precursor was synthesized to fabricate carbon molecular sieve membranes for hydrogen purification, and the membrane's hydrogen separation performance was optimized by adjusting the pyrolysis temperature. The CMSM derived at high pyrolysis temperature showed low carbon structural densification and excellent H2 selectivity.