Self-modified fabrication of inner skin ZIF-8 tubular membranes by a counter diffusion assisted secondary growth method

The ability to fabricate high-quality MOF-based membranes is critical and highly desired due to their outstanding performance in molecule separations and sensors. In this work, a water stable MOF, ZIF-8 is chosen as the typical example to validate a new self-modified counter diffusion assisted secondary growth method for the fabrication of inner skin tubular MOF membranes. The preparation route involves two main steps: counter diffusion for modifying the rough surface of industrial ceramic substrate (plugging pores in the ceramic tube) with homogenous ZIF-8 nanocrystals, and the secondary solvothermal growth for fabricating continuous ZIF-8 membranes on the inner surface of the tubular substrate. The ZIF-8 membranes prepared by this method are characterized in detail. The pre-modification process and the use of a low-reactivity growth solution containing zinc acetate favor the growth of dense ZIF-8 membrane in the solvothermal process.