Enhancement of Visible‐Light‐Driven Hydrogen Evolution Activity of 2D π‐Conjugated Bipyridine‐Based Covalent Organic Frameworks via Post‐Protonation

• Published in: Angewandte Chemie 2023-04, Vol.135 (15), p.n/a
• Main Authors: Dai, Lu, Dong, Anwang, Meng, Xiangjian, Liu, Huanyu, Li, Yueting, Li, Pengfei, Wang, Bo
• Format: Article
• Language: English
• Subjects: Bipyridine; Charge efficiency; Chemistry; Clean technology; COF; Evolution; Hydrogen evolution; Photocatalysis; Photocatalysts; Photocatalytic Hydrogen Evolution; Protonation; π-Conjugation
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202300224

Photocatalytic hydrogen (H2) evolution represents a promising and sustainable technology. Covalent organic frameworks (COFs)‐based photocatalysts have received growing attention. A 2D fully conjugated ethylene‐linked COF (BTT‐BPy‐COF) was fabricated with a dedicated designed active site. The introduced bipyridine sites enable a facile post‐protonation strategy to fine‐tune the actives sites, which results in a largely improved charge‐separation efficiency and increased hydrophilicity in the pore channels synergically. After modulating the degree of protonation, the optimal BTT‐BPy‐PCOF exhibits a remarkable H2 evolution rate of 15.8 mmol g−1 h−1 under visible light, which surpasses the biphenyl‐based COF 6 times. By using different types of acids, the post‐protonation is proved to be a potential universal strategy for promoting photocatalytic H2 evolution. This strategy would provide important guidance for the design of highly efficient organic semiconductor photocatalysts. The introduction of bipyridine motifs in the 2D conjugated covalent organic framework, 2D‐c‐COF, creates dedicated photoactive sites. Through a simple post‐protonation strategy, the photo‐generated electron–hole separation of 2D‐c‐COF was significantly enhanced and a hydrophilic pore channel was generated, which synergically lead to a significant improvement in photocatalytic hydrogen production.