Synergistic linkage engineering in covalent organic frameworks for boosting photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution using covalent organic frameworks (COFs) is promising for the energy transition and carbon neutrality. However, the efficiency of COF-based photocatalysts is often limited by the intrinsic properties of their linkages. Herein, we report synergistic linkage engineering in COFs to enhance photocatalytic hydrogen evolution. By converting imine linkage to 4-carboxyl-quinoline linkage, we have concurrently increased the pi-conjugation degree and the structural stability of the COF, as well as enhanced the hydrophilicity of its one-dimensional (1D) nanochannels. These modifications are advantageous for augmenting COF light absorption, facilitating the separation and migration of charge carriers and promoting the accessibility of water molecules within the channels. As a result, the obtained 4-carboxyl-quinoline-linked COF displayed an impressive hydrogen evolution rate of 55.83 +/- 1.26 mmol g-1 h-1 with excellent reusability and durability. This study not only advances the understanding the structure-performance relationships in COFs but also paves the way for the rational design of high-performance photocatalysts for sustainable energy applications.