Hierarchical and defect-free metal-organic framework membranes deep-rooted within flexible nanofiber substrate

Abstract

Defect-free MOFs membrane on flexible substrate is challenging and promising for industrial applications. In this work, electrospun nanofiber substrates were employed to construct deep-rooted and defect-free ZIF-8 membranes by a symbiotic layer composed of interpenetrated nanofibers and ZIF-8. Nanofibers provide sufficient nucleation sites to construct an interpenetrated “symbiotic layer”, which further supports ZIF-8 growing to be defect-free. Importantly, benefiting from this symbiotic layer, the rigidity difference between substrate and ZIF-8 is well balanced, resulting in ZIF-8 membrane deep-rooted within the support. Furthermore, tannic acid (TA), was combined to modulate the surface chemistry and inter-crystalline defects of ZIF-8 membranes. Finally, a hierarchical ZIF-8 membrane with nanofibers as flexible substrates were obtained. The prepared PAN/TA2-NZIF-80.25 membrane exhibits H2 permeance of 2408 GPU and H2/CO2 selectivity of 21.80. Specifically, compared with the reported MOFs membrane for H2 separation, the H2 permeance of this work locates in a very high region, while proper H2/CO2 separation factor is still remained, exceeding the 2008 upper bound of H2/CO2 separation. Importantly, this membrane presents stable microstructures and separation performance after twisting. The proposed deep-rooted and defect-free ZIF-8 membrane on flexible substrate is competitive to achieve industrial application.