Interfacial co-weaving of AO-PIM-1 and ZIF-8 in composite membranes for enhanced H2 purification

Abstract

Porous asymmetric composite membranes (ACMs) have attracted intensive attentions in energy-efficient gas separations. However, fabricating ACMs with defect-free interface and enhanced selectivity without sacrificing permeability remains great challenge. Herein, a major step towards this goal is proposed by employing an efficient co-weaving strategy to regulate interfacial microstructure of ACMs with bilayer geometry on porous substrates. The double layers are constructed by in-situ growing zeolitic imidazolate frameworks-8 (ZIF-8) on the surface of amidoxime-functionalized polymer of intrinsic microporosity-1 (AO-PIM-1) layer (denoted as AO-PIM-1@ZIF-8). The pre -designed amidoxime groups on the AO-PIM-1 backbone provide abundant coordinate sites for Zn (ΙΙ) ions, offering advantages for building a continuous membrane. Consequently, the obtained AO-PIM-1@ZIF-8 membrane demonstrates remarkable performance in H 2 /CO 2 separations, with the H 2 /CO 2 selectivity of 11.97 and the H 2 permeability of up to 5688 Barrer at 298 K and 1 bar. Both the H 2 permeability and H 2 /CO 2 selectivity exceed most of reported ACMs, and far surpassed Robeson’s 2008 upper bound by taking advantage of the molecular sieving effect of interfacial layer formed by co-weaving of AO-PIM-1 chains with ZIF-8. This is contributed either by position-space renormalisation for AO-PIM-1 chains or pore space partition in ZIF-8 at the interface. The study reports herein offer an alternative route to develop high-performance composite membranes for improved gas separations. • Two continuous composite membranes were prepared using a simple fabrication method. • Co-weaving strategy was used to eliminate the interfacial defects. • H 2 /CO 2 separations of the as-made membrane far exceeded Robeson’s 2008 upper bound. • This performance was from the molecular sieving effect of the interfacial layer.