Zhu Lin, Zhang Qian, Meng Fancheng, Li Mengqi, Liang Qifeng, Zhang Fan
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Electrochemical Energy Devices Research Center, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China.
Department of Physics, Shaoxing University, 508 Huanchengxi Road, Shaoxing, 312000, China.
Angew Chem Int Ed Engl. 2023 Oct 16;62(42):e202309125. doi: 10.1002/anie.202309125. Epub 2023 Sep 8.
Vinylene-linked covalent organic frameworks (COFs) are emerging as promising crystalline materials, but their narrow pore engineering is severely impeded by the weak reversibility of the carbon-carbon double bond formation reaction, which has led to less exploration of their ultramicroporous structures and properties. Herein, we developed a single aromatic ring-based tetratopic monomer, tetramethylpyrazine, which undergoes a smooth Knoevenegal condensation at its four arylmethly carbon atoms with linear aromatic dialdehyde monomers upon the self-catalyzed activation of pyridine nitrogen-containing monomers in the presence of an organic anhydride. This has resulted in the formation of two vinylene-linked COFs, which both crystallized in orthorhombic lattices, and layered in AA stacking fashions along the vertical directions. They exhibit high surface areas and well-tailored ultramicropore sizes up to 0.5 nm. The unique cross-linking mode at two pairs of para-positions of each pyrazine unit through carbon-carbon double bonds afford them with π-extended conjugation over the in-plane backbones and substantial semiconducting characters. The resultant COFs can be well-dispersed in water to form stable sub-microparticles with negative charges (zeta potentials: ca. -30 mV), and exhibiting tunable aggregation behaviors through protonation/deprotonation. As a consequence, they exhibit pore-size-dependent colorimetric responses to various anions with different pK values in high selectivity.
亚乙烯基连接的共价有机框架（COFs）正成为有前景的晶体材料，但其狭窄的孔道工程受到碳 - 碳双键形成反应弱可逆性的严重阻碍，这导致对其超微孔结构和性质的探索较少。在此，我们开发了一种基于单芳环的四连接单体四甲基吡嗪，在有机酐存在下，吡啶含氮单体自催化活化时，其四个芳基甲基碳原子与线性芳族二醛单体发生顺利的克诺文纳格尔缩合反应。这导致形成了两种亚乙烯基连接的COFs，它们均在正交晶格中结晶，并沿垂直方向以AA堆积方式分层。它们具有高表面积和高达0.5 nm的精心设计的超微孔尺寸。每个吡嗪单元在两对对位处通过碳 - 碳双键的独特交联模式赋予它们在平面内主链上的π扩展共轭和显著的半导体特性。所得的COFs可以很好地分散在水中，形成带负电荷的稳定亚微粒（zeta电位：约 - 30 mV），并通过质子化/去质子化表现出可调的聚集行为。因此，它们对具有不同pK值的各种阴离子表现出孔径依赖性的比色响应，具有高选择性。
