Poly-/metal-benzimidazole nano-composite membranes for hydrogen purification

Abstract

In this study, a novel scheme to fabricate nano-composite membrane materials containing fully dispersed nano-size zeolitic imidazolate frameworks (ZIFs) has been proposed for the first time. By mixing the as-synthesized ZIF-7 nano-particles without the traditional drying process with polybenzimidazole (PBI), the resultant membranes not only achieve an unprecedented ZIF-7 loading as high as 50 wt%, but also overcome the low permeability nature of PBI. The membranes exhibit characteristics of high transparency and mechanical flexibility, together with enhanced H2 permeability and ideal H2/CO2 permselectivity surpassing both neat PBI and ZIF-7 membranes. Advanced instrument analyses have confirmed the unique ZIF–polymer interface and elucidated the mixed matrix structure that contributes to the high ZIF loading and enhanced gas separation performance superior to the prediction from the Maxwell model. The high thermal stability, good dispersion of ZIF nanoparticles with minimal agglomeration and the attractive gas separation performance at elevated temperatures up to 180 °C indicate the practicability of this nano-composite material for hydrogen production and CO2 capture in realistic industrial applications under harsh and extreme environments.