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

Photocatalytic hydrogen (H-2) 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 H-2 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 H-2 evolution. This strategy would provide important guidance for the design of highly efficient organic semiconductor photocatalysts.

Automated summary

This study focuses on COFs-based photocatalysts, in which a 2D fully conjugated ethylene-linked COF (BTT-BPy-COF) with active sites was fabricated. A post-protonation strategy was employed to fine-tune the active sites, leading to improved charge-separation efficiency and increased hydrophilicity. The optimized BTT-BPy-PCOF exhibited a remarkable H-2 evolution rate under visible light, surpassing a biphenyl-based COF 6 times. Post-protonation was proven to be a potential universal strategy for promoting photocatalytic H-2 evolution and providing important guidance for the design of highly efficient organic semiconductor photocatalysts.