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

Abstract 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.