The PEK-c/ZIF-8 nanocomposite membranes are prepared by varying ZIF-8 loading. The ZIF-8 nanocrystals have a narrow size distribution in the range of 20–40 nm. The incorporation of ZIF-8 adjusts structure and properties of the PEK-c membrane. The ZIF-8 nanocrystals greatly enhance the permeability of the PEK-c membrane. The nanocomposite membranes exhibit a great potential in the MTBE purification.