Bay‐Monosubstitution with Electron‐Donating Group as an Efficiently Strategy to Functionalize Perylene Imide Polymer for Enhancing Photocatalytic Oxygen Evolution Activity

Abstract It is still a challenge to develop an organic conjugated photocatalyst with a high O₂ evolution rate. Functionalization organic polymer photocatalysts is an effective way to enhance photocatalytic performance. In this study, a series of perylene imide polymers (PDIs) are prepared by introducing different number of phenyl groups at bay position of PDI, and the influence of the number of substituents on charge separation and photocatalytic activity is investigated. It reveals that monosubstituted PDI exhibits the highest O₂ evolution rate of 2524.88 µmol g^–1 h^–1 under visible light illumination without any cocatalyst. The excellent performance ascribes to the push–pull intramolecular charge transfer and the high crystallinity, which significantly promote separation and transfer of photoinduced charge. However, the O₂ evolution rate dramatically drops with the number of substituent groups increase because introducing more groups at the bay position of PDI decreased charge local excitation of the PDI core and occupied the O₂ evolution active site. In addition, it is found that increasing the number of electron–donor substituent groups would seriously destroy the crystallinity, leading to a decrease in the O₂ evolution rate. This study highlights a reasonably structural modification strategy to enhance the O₂ evolution rate of the PDI polymer by electron‐donating group monosubstitution.