Porous Zn layers with different morphologies were designed and fabricated by sputtering from a Zn target using a DC power source, which were then annealed at different temperatures in the presence of oxygen to obtain porous zinc oxide layers. The effects of annealing on morphology, grain size and photoluminescence and photocatalysis were studied by XRD, SEM, UV-Vis spectrophotometer and PL. The results show that we are able to obtain thin, porous ZnO films with different morphologies, whose grain sizes and optical properties can be controlled by annealing temperature. Studies indicate that there is a strong correlation between the particle size, the PL signal, and therefore the presence of SOV and photocatalytic activity. We explain the activity of the photocatalysis based on the presence of surface-states evident in the photoluminescence. The photocatalytic efficiencies rival those of the nanoparticles, at much lower mass of the active material and without the need for solvent-based processing. Unlike other methods of obtaining ZnO, our method is unique in that it obtains pure material without organic envelopes as is the case in other wet methods, making ZnO thin films promising toward photocatalytic applications as well as beyond.