Morphology-tailoring of metal-organic frameworks (MOFs) is essential for their specific application in molecular-separation, catalysis, and drug-delivery. However, precision syntheses of uniform MOFs crystals with anisotropic shape are still challenging. Herein, a morphological map for monodisperse ZIF-8 crystals with five distinctive shapes was constructed in terms of the synthetic conditions. It was revealed that the formation mechanism for ZIF-8 crystals with various shapes is strongly dependent on the concentration of cetyltrimethylammonium bromide (CTAB) added, not limited to the traditional capping mechanism for MOFs and metal nanocrystals. The generality of this strategy was also verified through the successful morphology-controllable synthesis of ZIF-67 crystals. The effect of ZIF-8 morphology on separation performance of resulting cross-linked poly(ethylene oxide) (XLPEO)-based mixed-matrix membranes for CH/CH mixtures was also evaluated.