Fluorination‐Modulated Molecular Engineering in <i>β</i> ‐Ketoenamine Covalent Organic Frameworks toward Efficient Photocatalytic Hydrogen Evolution ^†

Comprehensive Summary Elucidating the structure–property–activity relationship in fluorinated COFs is crucial for advancing the rational design of high‐performance COF‐based photocatalysts. Despite its significance in guiding the development of next‐generation fluorinated COF photocatalysts, the interplay between the quantity, spatial distribution, and integration sites of functional groups within the COF's backbone at the molecular level remains underexplored. To address this, we propose a controlled fluorination molecular engineering strategy to systematically elucidate this relationship. By precisely tuning the number and positional arrangement of fluorine atoms, we effectively enhance carrier dynamics and interfacial reaction kinetics, thereby driving efficient photocatalytic hydrogen evolution reaction. Notably, the optimized TP‐COF‐F‐3 exhibited an apparent quantum yield of 4.09% at 500 nm, outperforming most reported COF‐based photocatalysts. These findings underscore a transformative approach to the molecular design of COF photocatalysts, providing insights for the development of advanced and sustainable photocatalytic systems.