Zhang Na, Wang Taisheng, Wu Xing, Jiang Chen, Chen Fang, Bai Wei, Bai Ruke
CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China Hefei 230026 P. R. China
Department of Chemistry, University of Tennessee Knoxville TN 37996 USA
RSC Adv. 2018 Jan 19;8(7):3803-3808. doi: 10.1039/c7ra09647j. eCollection 2018 Jan 16.
Recently, covalent organic nanosheets (CONs) have emerged as functional two-dimensional (2D) materials for versatile applications. Strong interaction among layers and the instability of borate ester in moisture are the major hurdles to obtain few layered boron-containing CONs by exfoliation of their bulk counterparts. In this paper, we report a facile approach for preparation of few layered borate ester-containing CONs based on electrostatic repulsion of ions. We incorporated organic ionic groups into porous covalent organic frameworks (COFs) and it has been proved that the COFs with quaternary ammonium group could self-exfoliate into few layered ionic covalent organic nanosheets (iCONs) in polar organic solvents. Interestingly, the morphology of the iCOFs-A could be changed from a multilayered aggregation to nanocapsules, or 2D sheets when solvents with different polarity were used. In contrast, non-ionic covalent organic frameworks COFs-B could not self-exfoliate in various solvents. In addition, the self-exfoliated nanosheets could be used to fabricate uniform thin films on SiO wafer and the film exhibited explicit optical and electrical properties.
最近，共价有机纳米片（CONs）已成为用于多种应用的功能性二维（2D）材料。层间的强相互作用以及硼酸酯在潮湿环境中的不稳定性是通过剥离其块状对应物来获得少层含硼CONs的主要障碍。在本文中，我们报道了一种基于离子静电排斥作用制备少层含硼酸酯CONs的简便方法。我们将有机离子基团引入多孔共价有机框架（COFs）中，并且已经证明带有季铵基团的COFs在极性有机溶剂中可以自剥离成少层离子共价有机纳米片（iCONs）。有趣的是，当使用不同极性的溶剂时，iCOFs-A的形态可以从多层聚集体变为纳米胶囊或二维片材。相比之下，非离子共价有机框架COFs-B在各种溶剂中都不能自剥离。此外，自剥离的纳米片可用于在SiO晶片上制备均匀薄膜，该薄膜表现出明显的光学和电学性质。
