Regulating the electronic structure of covalent organic frameworks via heterocyclic isomers for highly efficient photocatalytic H<sub>2</sub>O<sub>2</sub> generation.

Ju, Yujun; Lin, Hailong; Tan, Guoying; Su, Pingru; Wang, Zhe; Hu, Chenjia; Hou, Ruien; Hao, Tinglong et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

Covalent organic frameworks (COFs) are promising materials for photocatalytic hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) production. However, optimizing their electronic structures to enhance charge separation, oxygen adsorption, and reaction efficiency remains a challenge. Here we show that incorporating thiophene and furan isomeric units into the side chains of COFs enables precise tuning of their electronic structures and photocatalytic activity. Thiophene-containing frameworks exhibit superior charge separation and photocatalytic performance compared to those with furan, owing to stronger donor-acceptor interactions. A 2-substituted thiophene-based COF (DT<sub>2</sub>TA-TAPB), synthesized from 1,3,5-tris(4-aminophenyl)benzene and 2,5-di(thiophen-2-yl)terephthalaldehyde, exhibits reduced exciton binding energy, extended electron lifetime, and improved spatial charge separation. Mechanistic analysis reveals that the sulfur and adjacent carbon atoms within the thiophene of DT<sub>2</sub>TA-TAPB stabilize the endoperoxide intermediate, promoting a one-step, two-electron pathway for H<sub>2</sub>O<sub>2</sub> generation. Consequently, DT<sub>2</sub>TA-TAPB achieves H<sub>2</sub>O<sub>2</sub> yields of 10972 and 8587 μmol g<sup>-1</sup> h<sup>-1</sup> in 10% ethanol and pure water, respectively, outperforming most reported COF-based photocatalysts.