The etching process can be a useful method for the morphology control of nanostructures. Using precise experiments and theoretical calculations, we report a new ZnO etching process triggered by the reaction of ZnO with transition metal cations and demonstrate that the etching rate and direction could be controlled by varying the kind of transition metal cation. In addition, the developed etching process was introduced to form a thin and uniform ZnO layer, which was utilized for the fabrication of an improved propylene-selective ZIF-8 membrane via conversion seeding and secondary growth.