Xu Junsong, Yang Can, Bi Shuai, Wang Wenyan, He Yafei, Wu Dongqing, Liang Qifeng, Wang Xinchen, Zhang Fan
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China), .
College of Chemistry, State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou, 350002, China.
Angew Chem Int Ed Engl. 2020 Dec 21;59(52):23845-23853. doi: 10.1002/anie.202011852. Epub 2020 Oct 26.
The polarity of a semiconducting molecule affects its intrinsic photophysical properties, which can be tuned by varying the molecular geometry. Herein, we developed a D -symmetric tricyanomesitylene as a new monomer which could be reticulated into a vinylene-linked covalent organic framework (g-C N -COF) via Knoevenagel condensation with another D -symmetric monomer 2,4,6-tris(4'-formyl-biphenyl-4-yl)-1,3,5-triazine. Replacing tricyanomesitylene with a C -symmetric 3,5-dicyano-2,4,6-trimethylpyridine gave a less-symmetric vinylene-linked COF (g-C N -COF). The octupolar conjugated characters of g-C N -COF were reflected in its scarce solvatochromic effects either in ground or excited states, and endowed it with more promising semiconducting behavior as compared with g-C N -COF, such as enhanced light-harvesting and excellent photo-induced charge generation and separation. Along with the matched energy level, g-C N -COF enabled the two-half reactions of photocatalytic water splitting with an average O evolution rate of 51.0 μmol h g and H evolution rate of 2518.9 μmol h g . Such values are among the highest of state-of-the-art COF photocatalysts.
半导体分子的极性会影响其固有光物理性质，而这种性质可通过改变分子几何结构来调节。在此，我们开发了一种D对称的三氰基均三甲苯作为新单体，它可通过与另一种D对称单体2,4,6-三（4'-甲酰基-联苯-4-基）-1,3,5-三嗪进行克诺文纳格尔缩合反应，网状化形成一个亚乙烯基连接的共价有机框架（g-CN-COF）。用C对称的3,5-二氰基-2,4,6-三甲基吡啶取代三氰基均三甲苯，得到了一种对称性较低的亚乙烯基连接的COF（g-CN-COF）。g-CN-COF的八极共轭特性在其基态或激发态下的溶剂化显色效应都很微弱，与g-CN-COF相比，赋予了它更有前景的半导体行为，如增强的光捕获以及优异的光生电荷产生和分离能力。连同匹配的能级，g-CN-COF实现了光催化水分解的两个半反应，平均析氧速率为51.0 μmol h g，析氢速率为2518.9 μmol h g。这些值在最先进的COF光催化剂中处于最高水平。
