Three-Dimensional Fully Conjugated Covalent Organic Frameworks for Efficient Photocatalytic Water Splitting

Covalent organic frameworks (COFs) are promising photocatalystsfor water splitting, but their efficiency lags behind that of inorganiccounterparts partly due to the limited charge transport and opticalabsorption properties. To overcome this limitation, we proposed toemploy three-dimensional (3D) fully conjugated (FC) COFs with a topologicalassembly of cyclooctatetraene derivatives for photocatalytic watersplitting. On the basis of first-principles calculations, we demonstratedthat these 3D FC-COFs are semiconductors with exceptional charge transportand optical absorption properties. The carrier mobilities are comparableto those of inorganic semiconductors and superior to the record mobilityobserved in two-dimensional COFs. Additionally, the 3D FC-COFs exhibitbroad visible light absorption with direct band gaps and high opticalabsorption coefficients. Among them, two 3D FC-COFs are identifiedfor overall water splitting, while three others can facilitate thehydrogen evolution half-reaction. This study pioneers the design of3D FC-COF photocatalysts, potentially advancing their applicationsin photocatalysis and optoelectronics.