Polymer semiconductor photocatalysts usually suffer from the high exciton binding energy because of the low dielectric constant. Herein, two crystalline polymer photocatalyst prototypes, neutral covalent organic framework (COF) and ionic covalent organic framework (iCOF), were employed to investigate the exciton effect. After polarization by the ionic sites with high dipole moment, the iCOF endows a greatly increased dielectric constant to reach the low exciton binding energy of 23 meV, below the thermal energy under room temperature (k_BT, 26 meV). Thus, enhanced generation, separation, and transport of photogenerated charge carriers over the iCOF catalyst resulted in a hydrogen peroxide production rate of 10.01 mmol g^-1 h^-1 in the photocatalytic oxygen reduction coupling with water oxidation reaction, which is almost 7 times higher than the neutral COF under identical conditions. This work demonstrates a promising way to tune the dielectric properties of polymer photocatalysts in order to regulate the exciton effect and related photocatalytic behavior.

由于介电常数低，聚合物半导体光催化剂通常具有高激子结合能。在此，采用中性共价有机框架（COF）和离子共价有机框架（i COF）两种结晶聚合物光催化剂原型来研究激子效应。在具有高偶极矩的离子位点极化后，i COF 赋予了大大增加的介电常数，达到 23 meV 的低激子结合能，低于室温下的热能 ( k _B T, 26 meV)。因此，在i COF 催化剂上增强的光生电荷载流子的产生、分离和传输导致过氧化氢的产生率为 10.01 mmol g^-1 h ^-1在光催化氧还原耦合水氧化反应中，在相同条件下几乎是中性 COF 的 7 倍。这项工作展示了一种有前途的方法来调节聚合物光催化剂的介电性能，以调节激子效应和相关的光催化行为。