Three-Dimensional\nFully Conjugated Covalent Organic\nFrameworks for Efficient Photocatalytic Water Splitting

Abstract

Covalent organic frameworks (COFs) are promising photocatalysts\nfor water splitting, but their efficiency lags behind that of inorganic\ncounterparts partly due to the limited charge transport and optical\nabsorption properties. To overcome this limitation, we proposed to\nemploy three-dimensional (3D) fully conjugated (FC) COFs with a topological\nassembly of cyclooctatetraene derivatives for photocatalytic water\nsplitting. On the basis of first-principles calculations, we demonstrated\nthat these 3D FC-COFs are semiconductors with exceptional charge transport\nand optical absorption properties. The carrier mobilities are comparable\nto those of inorganic semiconductors and superior to the record mobility\nobserved in two-dimensional COFs. Additionally, the 3D FC-COFs exhibit\nbroad visible light absorption with direct band gaps and high optical\nabsorption coefficients. Among them, two 3D FC-COFs are identified\nfor overall water splitting, while three others can facilitate the\nhydrogen evolution half-reaction. This study pioneers the design of\n3D FC-COF photocatalysts, potentially advancing their applications\nin photocatalysis and optoelectronics.