Freezing assisted in situ growth of nano-confined ZIF-8 composite membrane for dye removal from water

In recent years, metal-organic framework (MOF) membranes have attracted much attention in many fields. However, the fabrication of MOF membrane with defect-free ultrathin separation layer on the surface of a substrate is very difficult. In this study, freezing assisted in situ growth strategy was used to prepare a nanoconfined ZIF-8 composite membrane on a porous ceramic substrate. The frozen alumina substrate with the metal ion ice crystal inside the pores was immersed in ligand solution for the growth of ZIF-8 crystals. Then, ZIF8 nanoparticles were grown inside the pores rather than on the surface of the substrate. The morphology and structure of the ZIF-8 particles and nano-confined composite membranes were characterized by XRD, SEM, FTIR, EDS, and nanoindentation. The obtained nano-confined ZIF-8 composite membrane exhibited excellent separation performance and stability for removing dyes from water. The influence of preparation conditions on membrane structure and property was also investigated. The freezing assisted method may provide an avenue for preparing MOF membranes in other fields.