Growth of ZIF-8 Membranes on Ceramic Hollow Fibers by Conversion of Zinc Oxide Particles

In this study, highly permeable alpha-Al2O3 hollow fibers containing ZnO particles have been successfully developed in one step for preparing ZIF-8 membranes. The Al2O3-ZnO hollow fibers consist of one thin sponge-like layer for depositing the ZIF-8 membrane and a number of self-organized finger-like pores for reducing gas permeation resistance. The effect of ZnO on the formation of the ZIF-8 membrane was determined. ZnO not only performs the function of seeding for the growth of the ZIF-8 membrane but also acts as the bonding bridge between the ZIF-8 membrane and the support to reinforce the membrane stability. Continuous and compact ZIF-8 membranes with a cross-linking structure on Al2O3-ZnO hollow fibers were successfully prepared by an in situ growth method. These ZIF-8 membranes displayed exceeding performance for hydrogen separation, good reproducibility, and outstanding mechanical stability. Conversion of ZnO to ZIF-8 membranes can effectively promote the nucleation and enhance the adhesion between ZIF-8 crystals and the support, thus improving the stability and reproducibility. This method can be easily scaled up and extended to prepare other metal-organic framework membranes because of their simplicity and high reproducibility.