The elaborated photonic architectures and unique light manipulation ability of diatoms provide inspirations for the design of efficient artificial photosynthetic systems. However, the biomimetic synthesis of artificial diatoms with accurate control over nanoscale geometry for scalable production has been a great challenge. Herein, diatom Coscinodiscus sp. is served as a model for the biomimetic production of artificial ceramic diatoms with multiscale photonic architectures for CO2 photoreduction. Optical finite-difference time-domain simulations are conducted to investigate the optical mechanisms on enhanced light harvesting and to establish a modified structural model. Electron Beam Lithography and Nanoimprint Lithography are applied to fabricate artificial TiO2 diatoms with elaborated periodic photonic structures and high surface areas (169.4 m(2) g(-1)). Artificial photosynthesis via CO2 reduction enhances CO and CH4 evolution on the artificial diatoms by up to 2.75- and 2.3-fold, respectively, compared with the corresponding powder sample. Furthermore, gas diffusion behaviors, closely related to the gas-phase reaction, are investigated by theoretical simulation to reveal the hierarchical structural effects on catalytic efficiency. This work provides a new pathway to design and biomimetic synthesis of artificial structures for enhanced performances.