A first example of an sp² carbon-conjugated three-dimensional (3D) covalent organic framework (COF) (BUCT-COF-4) is synthesized via the Knoevenagel condensation of the saddle-shaped aldehyde-substituted cyclooctatetrathiophene and 1,4-phenylenediacetonitrile. Ascribed to the extended π-conjugation and long-range ordered structures, BUCT-COF-4 displays high Hall electron mobility of 1.97 cm² V^–1 s^–1 at room temperature. After it is doped with iodine, the material not only exhibits an enhanced electron mobility up to 2.62 cm² V^–1 s^–1 in ambient air but also presents an unexpected metal-free ferromagnetic phase transition arising from the formation of aligned spins unidirectional across the whole sp² carbon-conjugated 3D framework. This is the first report of a ferromagnetic phenomenon in 3D COF materials, which would broaden promising applications and open a new frontier in COF materials.

中文翻译：

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三维 sp2 碳共轭共价有机框架

sp ²碳共轭三维（3D）共价有机骨架（COF）（BUCT-COF-4）的第一个例子是通过鞍形醛取代的环八四噻吩和1,4-苯二乙腈的Knoevenagel缩合合成的. 由于扩展的 π 共轭和长程有序结构，BUCT-COF-4在室温下显示出 1.97 cm ² V ^–1 s ^{–1 的}高霍尔电子迁移率。掺杂碘后，该材料不仅表现出高达 2.62 cm ² V ^–1 s ^–1的增强电子迁移率在环境空气中，但也呈现出意外的无金属铁磁相变，这是由于在整个 sp ²碳共轭 3D 框架中形成单向排列的自旋而引起的。这是 3D COF 材料中铁磁现象的首次报道，这将拓宽有前景的应用并开辟 COF 材料的新领域。