The crystallinity of semiconductors plays a vital role in boosting the separation and transportation of photogenerated carriers and their photocatalytic performance. However, organic semiconductors have relatively low crystallinity compared with their inorganic counterparts. Herein, we propose a novel strategy to improve the crystallinity of the fluorinated imine-linked covalent organic framework, TFA-TaPt-COF, by forming acetal between the aldehyde and ethanol. The TFA-TaPt-COF with higher crystallinity exhibited a broader absorption edge up to 650 nm, lower photoluminescence intensity, and 5 times higher photocatalytic H₂O₂ evolution rate than the one synthesized without using alcohol.