Fig. 1.

GVD fabrication of ultrathin ZIF-8 membrane. a Schematic of MOF membrane formation process. b Schematic illustration and chemical structure of Zn-based gel and crystalline structure of ZIF-8. Zn, O, C and N atoms are depicted in yellow, red, grey and blue, respectively. H atoms are not presented for clarity. Top view SEM images of c the PVDF hollow fibre and d the Zn-based gel layer. SEM images of e top and f cross-sectional view of the ZIF-8 membrane prepared with sol concentration of 1 U and coating time of 2 s. The images are coloured for clarity. Scale bar, 200 nm