Zhang Zixing, Meng Fancheng, Chi Xu, Jiao Yang, Xue Bai, Li Xiaomeng, Zhang Fan
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University (China), 800 Dongchuan Road, Shanghai, 200240, China.
Angew Chem Int Ed Engl. 2025 Feb 3;64(6):e202417805. doi: 10.1002/anie.202417805. Epub 2024 Nov 20.
Vinyl units intrinsically featuring less steric, nonpolarity, and unsaturated character, are well-known π-bridge used in the synthesis of high-performance semiconducting materials. Two-dimensional (2D) vinylene-linked covalent organic frameworks (COFs) represent a promising class of π-conjugated structures, however, the range of available monomers for the reversible formation of carbon-carbon double bonds remains limited. In this study, a new class of 2D vinylene-linked COFs were synthesized using dimethyldiketopyrrolopyrrole (DM-DPP) as the key monomer. The strong electron deficiency of diketopyrrolopyrrole (DPP) makes its methyl substituents readily activated upon the cocatalysis of L-proline and 4-dimethylaminopyridine in aqueous solution to conduct dynamic condensation with tritopic aromatic aldehydes. The resulting COFs crystallized in an eclipsed AA stacking arrangement and featured abundant, regular nanochannels. Their robust vinyl DPP-linking mode enhanced donor-π-acceptor conjugation and promoted π-stacked alignment along the vertical direction. Consequently, the synthesized COFs exhibited band gaps as narrow as 1.02 eV and demonstrated excellent light-harvesting capability across the visible to near-infrared I (NIR-I) regions. Furthermore, the COFs could be converted into free-standing thin pellets through simple pressure casting, and show excellent photothermal response and cycling stability under different light sources.
乙烯基单元本质上具有较小的空间位阻、非极性和不饱和特性，是合成高性能半导体材料中常用的π桥。二维（2D）亚乙烯基连接的共价有机框架（COF）代表了一类很有前景的π共轭结构，然而，可用于可逆形成碳 - 碳双键的单体范围仍然有限。在本研究中，使用二甲基二酮吡咯并吡咯（DM - DPP）作为关键单体合成了一类新型的二维亚乙烯基连接的COF。二酮吡咯并吡咯（DPP）的强缺电子性使得其甲基取代基在L - 脯氨酸和4 - 二甲氨基吡啶的共催化下，在水溶液中易于活化，从而与三官能团芳香醛进行动态缩合。所得的COF以重叠的AA堆积排列结晶，并具有丰富、规则的纳米通道。它们坚固的乙烯基DPP连接模式增强了供体 - π - 受体共轭，并促进了沿垂直方向的π堆积排列。因此，合成的COF表现出低至1.02 eV的带隙，并在可见光到近红外I（NIR - I）区域表现出优异的光捕获能力。此外，通过简单的压片法可将COF转化为独立的薄片，并且在不同光源下表现出优异的光热响应和循环稳定性。
