Muggli Katharina, Spies Laura, Bessinger Derya, Auras Florian, Bein Thomas
Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany.
Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
ACS Nanosci Au. 2023 Feb 17;3(2):153-160. doi: 10.1021/acsnanoscienceau.2c00049. eCollection 2023 Apr 19.
Thienothiophene thienoisoindigo (ttTII)-based covalent organic frameworks (COFs) have been shown to offer low band gaps and intriguing optical and electrochromic properties. So far, only one tetragonal thienothiophene thienoisoindigo-based COF has been reported showing stable and fast electrochromism and good coloration efficiencies. We have developed two novel COFs using this versatile and nearly linear ttTII building block in a tetragonal and a hexagonal framework geometry to demonstrate their attractive features for optoelectronic applications of thienoisoindigo-based COFs. Both COFs exhibit good electrical conductivities, show promising optical absorption features, are redox-active, and exhibit a strong electrochromic behavior when applying an external electrical stimulus, shifting the optical absorption even farther into the NIR region of the electromagnetic spectrum and achieving absorbance changes of up to 2.5 OD. Cycle-stable cyclic voltammograms with distinct oxidation and reduction waves reveal excellent reversibility and electrochromic switching over 200 cycles and confirm the high stability of the frameworks. Furthermore, high coloration efficiencies in the NIR region and fast switching speeds for coloration/decoloration as fast as 0.75 s/0.37 s for the Cz-ttTII COF and 0.61 s/0.29 s for the TAPB-ttTII COF at 550 nm excitation were observed, outperforming many known electrochromic materials, and offering options for a great variety of applications, such as stimuli-responsive coatings, optical information processing, or thermal control.
基于噻吩并噻吩噻吩并异吲哚（ttTII）的共价有机框架（COF）已被证明具有低带隙以及引人入胜的光学和电致变色特性。到目前为止，仅报道了一种基于噻吩并噻吩噻吩并异吲哚的四方COF，其显示出稳定且快速的电致变色以及良好的着色效率。我们使用这种通用且近乎线性的ttTII构建单元，在四方和六边形框架几何结构中开发了两种新型COF，以展示它们在基于噻吩并异吲哚的COF光电子应用中的诱人特性。两种COF均表现出良好的电导率，具有有前景的光吸收特性，具有氧化还原活性，并且在施加外部电刺激时表现出强烈的电致变色行为，将光吸收进一步移至电磁光谱的近红外区域，并实现高达2.5 OD的吸光度变化。具有明显氧化和还原波的循环稳定循环伏安图显示出在200个循环中具有出色的可逆性和电致变色切换，并证实了框架的高稳定性。此外，在550 nm激发下，观察到近红外区域的高着色效率以及Cz-ttTII COF的着色/褪色快速切换速度高达0.75 s/0.37 s，TAPB-ttTII COF的为0.61 s/0.29 s，优于许多已知的电致变色材料，并为多种应用提供了选择，例如刺激响应涂层、光学信息处理或热控制。
