聚苝酰亚胺（PDI）已被证明是光催化析氧的优异候选材料，但是其光催化析氧反应活性的来源仍需要进一步的探索。本文基于X射线衍射谱解析了PDI的晶体和原子结构，并利用第一原理密度泛函理论计算阐明其电子结构，证实PDI具有适合光催化析氧反应的能带结构和优异的电子激发效率。晶体轨道哈密顿布居分析证实，共轭结构中尿素和苝环之间的羰基氧原子是光催化析氧的反应活性位点。反应自由能变化计算表明， PDI表面的光催化析氧反应遵循H₂O → *OH → *O → *OOH → *O₂的路径，过电位为0.81 V。通过对原子结构和电子结构的理论研究，本文阐明了PDI光催化析氧反应的活性起源，为高效光催化析氧聚合物光催化剂的理性设计和改性提供理论指导。

Polymeric perylene diimide (PDI) has been evidenced as a good candidate for photocatalytic water oxidation, yet the origin of the photocatalytic oxygen evolution activity remains unclear and need further exploration. Herein, with crystal and atomic structures revealed from the X-ray diffraction pattern, the electronic structure is theoretically illustrated by the first-principles density functional theory calculations, suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution. It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis. The reaction free energy changes calculations reveal that the oxygen evolution reaction should follow the pathway of H₂O → *OH → *O → *OOH → *O₂ with an overpotential of 0.81 V. Through an in-depth theoretical computational analysis in the atomic and electronic structures, the origin of photocatalytic oxygen evolution activity for PDI is well illustrated, which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.