The support should promote the heterogeneous nucleation of ZIFs crystals. The bare support lacks heterogeneous nucleation. Thus, surface modification of the support is usually required to create active sites for crystal nucleation. In fact, α-alumina supports were modified with organic linkers , polymer , or ZnO . ZnO or organic linkers can be used as sacrificial templates for the nucleation and growth of ZIFs crystals . The sacrificial templates enable the formation of smooth layers of ZIFs crystals. The ceramic substrate can also be modified chemically with 3aminopropyltriethoxysilane (APTES) . APTES molecules act as a binder between the membrane layer, the support, and the ZIF-22 crystals . It forms a covalent bond between the ethoxy groups of APTES react and the surface hydroxyl groups of cerium support, such as Al2O3 . The presence of functional groups of the support and the surface modification ensure effective heterogeneous sites for developing continuous layers of ZIFs materials on the substrate .