In this contribution, a novel mesoporous CuO/ZnO heterojunctions were fabricated and designed through a wet chemical process in the presence of F127 surfactant. TEM image of mesoporous CuO/ZnO heterojunction showed a homogeneous size distribution with uniform spherical with particles size ~20 nm. The surface area of pristine ZnO NPs was estimated to be 200 m2/g, which reduced to 175 m2/g at 4% CuO/ZnO heterojunction. The synthesized CuO/ZnO heterojunctions were exhibited to effectively reduction and removal of Mercury (Hg(II)) ions through visible light. The optimized mesoporous 3% ZnO/CuO heterojunction exhibited the highest photoreduction efficiency compared to commercial P-25 and pristine ZnO NPs. The photoreduction/removal efficiency of Hg(II) over 3%CuO/ZnO heterojunction was reached up to 100% within 60 min, which is ~14 and ~24 times higher than P-25 and pristine ZnO NPs, respectively. The rate constant of mesoporous 3% ZnO/CuO heterojunction is better 30 and 54 order magnitudes than that compared with P-25 and pristine ZnO NPs, respectively. This is explained by the mesoporous CuO/ZnO heterojunctions greatly promotes the utilization light rate owing to its characteristic architecture, increases the surface area and pore volumes, promoting mass diffusion and providing more active sites, enhances the photoinduced electrons transfer the as a result of the formation of p-n types CuO/ZnO heterojunctions. Nevertheless, the photocatalysts were readily reused and recovered for five cycles without significant loss of photoreduction efficiency.