Kim Young Hyun, Jeon Jong-Pil, Kim Yongchul, Noh Hyuk-Jun, Seo Jeong-Min, Kim Jiwon, Lee Geunsik, Baek Jong-Beom
School of Energy and Chemical Engineering/Center for Dimension-Controllable Organic Frameworks, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST, Ulsan, 44919, Republic of Korea.
Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST, Ulsan, 44919, Republic of Korea.
Angew Chem Int Ed Engl. 2023 Sep 4;62(36):e202307991. doi: 10.1002/anie.202307991. Epub 2023 Jul 28.
Covalent organic frameworks (COFs) have emerged as a promising platform for photocatalysts. Their crystalline porous nature allows comprehensive mechanistic studies of photocatalysis, which have revealed that their general photophysical parameters, such as light absorption ability, electronic band structure, and charge separation efficiency, can be conveniently tailored by structural modifications. However, further understanding of the relationship between structure-property-activity is required from the viewpoint of charge-carrier transport, because the charge-carrier property is closely related to alleviation of the excitonic effect. In the present study, COFs composed of a fixed cobalt (Co) porphyrin (Por) centered tetraamine as an acceptor unit with differently conjugated di-carbaldehyde based donor units, such as benzodithiophene (BDT), thienothiophene (TT), or phenyl (TA), were synthesized to form Co-Por-BDT, Co-Por-TT, or Co-Por-TA, respectively. Their photocatalytic activity for reducing carbon dioxide into carbon monoxide was in the order of Co-Por-BDT>Co-Por-TT>Co-Por-TA. The results indicated that the excitonic effect, associated with their charge-carrier densities and π-conjugation lengths, was a significant factor in photocatalysis performance.
共价有机框架（COF）已成为一种很有前景的光催化剂平台。其晶体多孔性质使得对光催化进行全面的机理研究成为可能，这些研究表明，通过结构修饰可以方便地调整其一般光物理参数，如光吸收能力、电子能带结构和电荷分离效率。然而，从电荷载流子传输的角度来看，还需要进一步了解结构-性质-活性之间的关系，因为电荷载流子性质与激子效应的缓解密切相关。在本研究中，合成了由固定的以钴（Co）卟啉（Por）为中心的四胺作为受体单元，与不同共轭的基于二醛的供体单元（如苯并二噻吩（BDT）、噻吩并噻吩（TT）或苯基（TA））组成的COF，分别形成Co-Por-BDT、Co-Por-TT或Co-Por-TA。它们将二氧化碳还原为一氧化碳的光催化活性顺序为Co-Por-BDT>Co-Por-TT>Co-Por-TA。结果表明，与它们的电荷载流子密度和π共轭长度相关的激子效应是光催化性能的一个重要因素。
