Mi Zhen, Zhou Ting, Weng Weijun, Unruangsri Junjuda, Hu Ke, Yang Wuli, Wang Changchun, Zhang Kai A I, Guo Jia
State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, 2005 Songhu Road, Shanghai, 200438, China.
Department of Chemistry, Chulalongkorn University, Phayathai Road, Bangkok, 10330, Thailand.
Angew Chem Int Ed Engl. 2021 Apr 19;60(17):9642-9649. doi: 10.1002/anie.202016618. Epub 2021 Mar 11.
Electron transfer is the rate-limiting step in photocatalytic water splitting. Viologen and its derivatives are able to act as electron-transfer mediators (ETMs) to facilitate the rapid electron transfer from photosensitizers to active sites. Nevertheless, the electron-transfer ability often suffers from the formation of a stable dipole structure through the coupling between cationic-radical-containing viologen-derived ETMs, by which the electron-transfer process becomes restricted. Herein, cyclic diquats, a kind of viologen-derived ETM, are integrated into a 2,2'-bipyridine-based covalent organic framework (COF) through a post-quaternization reaction. The content and distribution of embedded diquat-ETMs are elaborately controlled, leading to the favorable site-isolated arrangement. The resulting materials integrate the photosensitizing units and ETMs into one system, exhibiting the enhanced hydrogen evolution rate (34600 μmol h g ) and sustained performances when compared to a single-module COF and a COF/ETM mixture. The integration strategy applied in a 2D COF platform promotes the consecutive electron transfer in photochemical processes through the multi-component cooperation.
电子转移是光催化水分解中的限速步骤。紫精及其衍生物能够作为电子转移介质（ETM），促进电子从光敏剂快速转移到活性位点。然而，电子转移能力常常因含阳离子自由基的紫精衍生ETM之间的偶联形成稳定的偶极结构而受到影响，电子转移过程因此受限。在此，通过后季铵化反应将一种紫精衍生ETM——环状双季铵盐，整合到基于2,2'-联吡啶的共价有机框架（COF）中。精心控制嵌入的双季铵盐ETM的含量和分布，实现了有利的位点隔离排列。所得材料将光敏单元和ETM整合到一个体系中，与单模块COF和COF/ETM混合物相比，析氢速率提高（34600 μmol h g ）且性能持续稳定。应用于二维COF平台的整合策略通过多组分协同促进了光化学过程中的连续电子转移。
