Photocatalytic water splitting and purification become more and more important to tackle the severe energy and environment challenges in modern society. In this study, carbon- and nitrogen-modified ZnO photocatalysts were prepared by the controlled thermal decomposition of zeolitic imidazolate framework (ZIF)-8. ZIF-8 carbonization in a nitrogen atmosphere confined highly dispersive Zn into porous carbon, and the followed calcination in air induced the formation of nanosized ZnO photocatalysts. The physicochemical properties of the photocatalysts were investigated by a variety of characterization techniques, and the photocatalytic performances were evaluated in both oxygen evolution and degradation of dye under solar light. It was found that the two-step synthesis delivered better photocatalyst materials than that from one-step synthesis (directly annealing in nitrogen or air). The co-existence of nitrogen and carbon in ZnO was suggested to be favorable to enhanced photo catalysis.