Enhancing Built-in Electric Fields in Covalent Organic Frameworks With High Surface Area and High Stability for...

The built-in electric field (BIEF) is a fundamental driving force governing the separation, transfer, and lifetime of photogenerated charge carriers, thereby dictating the activity of photocatalysts. Herein, a local p-π conjugation regulation strategy was developed to tailor the BIEF in covalent organic frameworks (COFs) as advanced photocatalysts. Three COFs of NKU-191, NKU-191-OH, and NKU-191-OMe, featuring robust acid-base resistance, high stability, and high specific surface area, were synthesized via Schiff base reactions under mild conditions. Without altering their intrinsic backbone structure, the photocatalytic hydrogen evolution activity was enhanced from 4.8 mmol g^-1 h^-1 (NKU-191) to 35.6 mmol g^-1 h^-1 (NKU-191-OMe). Comprehensive characterizations and systematic analysis revealed that the introduction of electron-donating groups effectively strengthens the local p-π conjugation within the COF skeletons, which in turn reinforces the BIEF intensity. This enhanced BIEF accelerates the separation and migration kinetics of photogenerated charge carriers, thereby enabling remarkable photocatalytic activity. This work not only establishes a facile synthetic protocol for synthesizing COFs with high specific surface areas and high stability but also clarifies the regulatory role of local p-π conjugation in regulating the BIEF intensity of COF-based photocatalysts, providing valuable insights for promoting the rational design and development of high-performance COF-based photocatalysts.