The interesting g-C₃N₄ nanosheet morphology has drawn huge attention in photocatalytic applications because of its special features. Nonetheless, the relative activity of these nanosheets is still controversial due to the low available active sites and the high recombination probability of photo-induced charge carriers. In this work, in situ sol–gel approach was applied to synthesize holey g-C₃N₄ nanosheets/hydroxyapatite (HAp) nanospheres with plentiful in-plane holes. Herein, the presence of Ca²⁺ plays a key role in the formation of holey defects on 2D g-C₃N₄. In-plane holes provide nanosheets with more active edges and diffusion channelsv, resulting in a tremendous enhanced mass and photo-induced charge transfer speed. Moreover, the holes make highly numbered boundaries, which lead to the prevention of aggregation. On the other hand, distributed nano-HAp spheres on these nanosheets can form effective heterojunctions having high photo-degradation ability of pollutants. Intrinsic O-vacancies inside HAp unit cells mainly affect the capture of photogenerated electrons, pollutant molecules, and O₂ gas. The synergistic presence of O-vacancies and holey defects (C-vacancies) on 2D g-C₃N₄ plays a key role in raising the photocatalytic performance of holey g-C₃N₄/HAp. It can be concluded that the proposed preparation method is a promising approach for simultaneous synthesis of holey g-C₃N₄ and surface heterojunctions of Ca-based materials. This new structure has shown significant degradation ability of bisphenol A, a prominent pollutant, with a low amount (0.01 g) and short time.