Winter Alena, Hamdi Farzad, Eichhöfer Andreas, Saalwächter Kay, Kastritis Panagiotis L, Haase Frederik
Institute of Chemistry, Faculty of Natural Sciences II, Martin-Luther-Universität Halle-Wittenberg Halle/Saale Germany
Department of Integrative Structural Biochemistry, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg Halle/Saale Germany.
Chem Sci. 2024 Aug 13;15(35):14449-57. doi: 10.1039/d4sc03461a.
Covalent Organic Frameworks (COFs) exhibiting kagome () structures are promising crystalline porous materials with two distinct pores. However, there are no reliable synthetic methods to exclusively target the over the polymorphic square-lattice () structure. To address this, we introduce a linker design strategy featuring bulky functional groups, which through steric interactions can hinder the net formation, thereby leading to a structure. By rigid attachment of the methyl benzoate groups to a tetradentate COF linker, steric interactions with neighbouring linkers depending on the pore size become possible. The steric interaction was tuned by varying the complementary bidentate linear linker lengths, where the shorter phenylenediamine linker leads to steric hindrance and the formation of the lattice, while with the longer benzidine linker, steric interaction is reduced leading to the lattice. Thus, control over the net can be exerted through steric interaction strengths. Additionally, structural analysis revealed the formation of the COF with an unusual ABC stacking, leading to pearl string type pores instead of two distinct pore sizes. This COF system shows that steric interaction-driven design enhances control over COF structures, expanding the design toolbox, but also provides valuable insights into network formation and polymorphism.
具有戈薇（）结构的共价有机框架（COF）是一类很有前景的晶体多孔材料，具有两种不同的孔结构。然而，目前尚无可靠的合成方法能够专门合成戈薇结构而非其多晶型的方晶格（）结构。为解决这一问题，我们引入了一种带有庞大官能团的连接体设计策略，该策略通过空间相互作用阻碍方晶格网络的形成，从而得到戈薇结构。通过将苯甲酸甲酯基团刚性连接到四齿COF连接体上，根据孔径大小与相邻连接体之间的空间相互作用成为可能。通过改变互补的双齿线性连接体长度来调节空间相互作用，其中较短的苯二胺连接体导致空间位阻并形成方晶格，而使用较长的联苯胺连接体时，空间相互作用减弱，导致形成戈薇晶格。因此，可以通过空间相互作用强度来控制晶格网络。此外，结构分析表明形成了具有不寻常ABC堆积的戈薇COF，导致形成珍珠串型孔而非两种不同的孔径。该COF体系表明，空间相互作用驱动的设计增强了对COF结构的控制，扩展了设计工具箱，同时也为网络形成和多晶型提供了有价值的见解。
