Fully conjugated 3D covalent organic frameworks with electron donor-acceptor alternated structures for...

Covalent organic frameworks (COFs) can serve as promising catalysts for photosynthesis of hydrogen peroxide (H₂O₂), of which the performances mostly rely on their ordered π-conjugated skeletons and electronic structures that promote the formation and separation of excitons. Designing electron donor (D)-acceptor (A) alternated structures within the fully π-conjugated frameworks has been demonstrated to be the most powerful strategy to develop high-performance photocatalysts, while most current cases are focused on two-dimensional (2D) COFs. Here we design and synthesize a series of D-A type fully conjugated 3D COFs by combining the saddle-shaped cyclooctatetrathiophene derivative with hierarchical electron donor units that consist of benzene, naphthalene and pyrene. The as-synthesized naphthalene-contained 3D COF exhibits an exceptional photocatalytic H₂O₂ production performance, which is almost 8 times higher than that of the non-conjugated 3D counterpart. Impressively, under the condition of actual seawater and air without sacrificial agents, it could deliver steady production over 155 h in a continuous-flow photocatalytic reactor system. Our work not only provides insight into the regulation of D-A electrical structures of 3D COFs for efficient photocatalysis, but also demonstrates that the semiconducting fully conjugated 3D COFs could be an ideal platform for green and sustainable development.