School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, 30332-0400, USA.
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA.
Adv Mater. 2020 Jan;32(2):e1905776. doi: 10.1002/adma.201905776. Epub 2019 Nov 25.
Imine-linked 2D covalent organic frameworks (COFs) form more rapidly than previously reported under Brønsted acid-catalyzed conditions, showing signs of crystallinity within a few minutes, and maximum crystallinity within hours. These observations contrast with the multiday reaction times typically employed under these conditions. In addition, vacuum activation, which is often used to isolate COF materials significantly erodes the crystallinity and surface area of the several isolated materials, as measured by N sorption and X-ray diffraction. This loss of material quality during isolation for many networks has historically obscured otherwise effective polymerization conditions. The influence of the activation procedure is characterized in detail for three COFs, with the commonly used 1,3,5-tris(4-aminophenyl)benzene-terephthaldehyde network (TAPB-PDA COF), the most prone to pore collapse. When the networks are activated carefully, rapid COF formation is general for all five of the imine-linked 2D COFs studied, with all exhibiting excellent crystallinity and surface areas, including the highest surface areas reported to date for three materials. Furthermore, to simplify the workup of COF materials, a simple nitrogen flow method provides high-quality materials without the need for specialized equipment. These insights have important implications for studying and understanding how 2D COFs form.
亚胺键连接的二维共价有机框架（COFs）在布朗斯台德酸催化条件下的形成速度比以前报道的要快，在几分钟内就表现出结晶迹象，几小时内就达到最大结晶度。这些观察结果与在这些条件下通常采用的多日反应时间形成对比。此外，真空活化，常用于分离 COF 材料，会显著侵蚀几个分离材料的结晶度和比表面积，这可以通过氮气吸附和 X 射线衍射来测量。在许多网络的分离过程中，这种材料质量的损失在历史上掩盖了原本有效的聚合条件。详细研究了三种 COFs 的活化程序的影响，其中最容易发生孔塌陷的是常用的 1,3,5-三(4-氨基苯基)苯-对苯二甲酸亚胺键连接的二维 COF（TAPB-PDA COF）。当小心地对网络进行活化时，所有五种亚胺键连接的二维 COFs 的 COF 快速形成是普遍的，所有 COFs 都表现出极好的结晶度和比表面积，包括三种材料中报道的最高比表面积。此外，为了简化 COF 材料的后处理，简单的氮气流方法提供了高质量的材料，而无需特殊设备。这些见解对研究和理解二维 COFs 的形成具有重要意义。
