Rotter Julian M, Guntermann Roman, Auth Michael, Mähringer Andre, Sperlich Andreas, Dyakonov Vladimir, Medina Dana D, Bein Thomas
Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München Butenandtstraße 5-13 (E) 81377 Munich Germany
Experimental Physics VI, Julius-Maximilians-Universität Würzburg 97074 Würzburg Germany.
Chem Sci. 2020 Oct 27;11(47):12843-12853. doi: 10.1039/d0sc03909h.
Covalent organic frameworks (COFs) define a versatile structural paradigm combining attractive properties such as crystallinity, porosity, and chemical and structural modularity which are valuable for various applications. For the incorporation of COFs into optoelectronic devices, efficient charge carrier transport and intrinsic conductivity are often essential. Here, we report the synthesis of two imine-linked two-dimensional COFs, WTA and WBDT, featuring a redox-active Wurster-type motif based on the twisted tetragonal ,,','-tetraphenyl-1,4-phenylenediamine node. By condensing this unit with either terephthalaldehyde (TA) or benzodithiophene dialdehyde (BDT), COFs featuring a dual-pore kagome-type structure were obtained as highly crystalline materials with large specific surface areas and mesoporosity. In addition, the experimentally determined high conduction band energies of both COFs render them suitable candidates for oxidative doping. The incorporation of a benzodithiophene linear building block into the COF allows for high intrinsic macroscopic conductivity. Both anisotropic and average isotropic electrical conductivities were determined with van der Pauw measurements using oriented films and pressed pellets, respectively. Furthermore, the impact of different dopants such as FTCNQ, antimony pentachloride and iodine on the conductivities of the resulting doped COFs was studied. By using the strong organic acceptor FTCNQ, a massive increase of the radical cation density (up to 0.5 radicals per unit cell) and long-term stable electrical conductivity as high as 3.67 S m were achieved for the anisotropic transport in an oriented film, one of the highest for any doped COF to date. Interestingly, no significant differences between isotropic and anisotropic charge transport were found in films and pressed pellets. This work expands the list of possible building nodes for electrically conducting COFs from planar systems to twisted geometries. The achievement of high and stable electrical conductivity paves the way for possible applications of new COFs in organic (opto)electronics.
共价有机框架（COFs）定义了一种通用的结构范式，它结合了诸如结晶性、孔隙率以及化学和结构模块化等吸引人的特性，这些特性对于各种应用都很有价值。为了将COFs纳入光电器件中，有效的电荷载流子传输和本征电导率通常至关重要。在此，我们报告了两种亚胺连接的二维COFs，即WTA和WBDT的合成，它们基于扭曲的四方、、、'-四苯基-1,4-苯二胺节点具有氧化还原活性的沃斯特型基序。通过将该单元与对苯二甲醛（TA）或苯并二噻吩二醛（BDT）缩合，获得了具有双孔 kagome 型结构的COFs，它们是具有大比表面积和介孔率的高度结晶材料。此外，两种COFs通过实验测定的高导带能量使其成为氧化掺杂的合适候选材料。将苯并二噻吩线性结构单元纳入COF可实现高本征宏观电导率。分别使用取向膜和压制颗粒通过范德堡测量法测定了各向异性和平均各向同性电导率。此外，还研究了不同掺杂剂（如FTCNQ、五氯化锑和碘）对所得掺杂COFs电导率的影响。通过使用强有机受体FTCNQ，对于取向膜中的各向异性传输，实现了自由基阳离子密度的大幅增加（高达每晶胞0.5个自由基）以及高达3.67 S m的长期稳定电导率，这是迄今为止任何掺杂COF中最高的之一。有趣的是，在膜和压制颗粒中未发现各向同性和各向异性电荷传输之间的显著差异。这项工作将导电COFs可能的构建节点列表从平面系统扩展到了扭曲几何结构。高且稳定的电导率的实现为新型COFs在有机（光）电子学中的可能应用铺平了道路。
