Abstract Covalent organic framework is a designable and versatile platform for preparation of various functional materials including conventional gas adsorption and separation materials, catalysis matrix, and photoelectric materials, etc. The covalent organic framework with redox building block and conjugated molecular structure can be viewed as a conjugated polymer with ordered porous structure. In this paper, we synthesized a Schiff base type conjugated organic framework (COF) by a solvothermal method in a common Teflon-lined stainless steel autoclave. The reversible reaction of dynamic imine bonds in solvothermal process induces the morphology transform of COF from nanoparticle to nanofiber. Besides of its structure, morphology, nanofiber-formation mechanism and electrochemical properties, the electrochromic properties of COF were investigated for the first time. Owing to the redox building block of triphenylamine, the COF possesses reversibly electrochromic behavior caused by reversibly redox reaction and band gap change of triphenylamine unit. Under step potentials between −2.5 V and 2.5 V, the COF can switch between bright yellow color and brown color. The stability test shows that the device can reversibly switch with stable contrast after slight decay at the initiated cycles. In consideration of abundant options of building units with redox feature, the COF based electrochromic materials with rich color and novel properties can be expected.

中文翻译：

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席夫碱型共轭有机骨架纳米纤维：溶剂热合成和电致变色性能

摘要 共价有机骨架是一种可设计的通用平台，可用于制备各种功能材料，包括常规气体吸附分离材料、催化基质和光电材料等。具有有序多孔结构的共轭聚合物。在本文中，我们在普通的特氟龙内衬不锈钢高压釜中通过溶剂热法合成了席夫碱型共轭有机骨架（COF）。溶剂热过程中动态亚胺键的可逆反应诱导了 COF 从纳米颗粒到纳米纤维的形态转变。除了其结构、形貌、纳米纤维形成机制和电化学性能外，首次研究了COF的电致变色性能。由于三苯胺的氧化还原结构单元，COF 具有可逆氧化还原反应和三苯胺单元带隙变化引起的可逆电致变色行为。在-2.5 V和2.5 V之间的阶跃电位下，COF可以在亮黄色和棕色之间切换。稳定性测试表明，该器件在启动周期略有衰减后，可以以稳定的对比度可逆地切换。考虑到具有氧化还原特性的构建单元的丰富选择，可以期待具有丰富色彩和新颖性能的COF基电致变色材料。COF具有可逆氧化还原反应和三苯胺单元带隙变化引起的可逆电致变色行为。在-2.5 V和2.5 V之间的阶跃电位下，COF可以在亮黄色和棕色之间切换。稳定性测试表明，该器件在启动周期略有衰减后，可以以稳定的对比度可逆地切换。考虑到具有氧化还原特性的构建单元的丰富选择，可以期待具有丰富色彩和新颖性能的COF基电致变色材料。COF具有可逆氧化还原反应和三苯胺单元带隙变化引起的可逆电致变色行为。在-2.5 V和2.5 V之间的阶跃电位下，COF可以在亮黄色和棕色之间切换。稳定性测试表明，该器件在启动周期略有衰减后，可以以稳定的对比度可逆地切换。考虑到具有氧化还原特性的构建单元的丰富选择，可以期待具有丰富色彩和新颖性能的COF基电致变色材料。