Maschita Johannes, Banerjee Tanmay, Lotsch Bettina V
Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Department of Chemistry, University of Munich (LMU), Butenandtstraße 5-13, 81377 München, Germany.
Chem Mater. 2022 Mar 8;34(5):2249-2258. doi: 10.1021/acs.chemmater.1c04051. Epub 2022 Feb 17.
Covalent organic frameworks (COFs) are an extensively studied class of porous materials, which distinguish themselves from other porous polymers in their crystallinity and high degree of modularity, enabling a wide range of applications. However, the established synthetic protocols for the synthesis of stable and crystalline COFs, such as imide-linked COFs, often requires the use of high boiling solvents and toxic catalysts, making their synthesis expensive and environmentally harmful. Herein, we report a new environmentally friendly strategy-an alcohol-assisted hydrothermal polymerization approach (aaHTP) for the synthesis of a wide range of crystalline and porous imide-linked COFs. This method allows us to gain access to new COFs and to avoid toxic solvents by up to 90% through substituting commonly used organic solvent mixtures with water and small amounts of n-alcohols without being restricted to water-soluble linker molecules. Additionally, we use the aaHTP to demonstrate an eco-friendly COF-to-COF transformation of an imine-linked COF into a novel imide-linked COF via linkage replacement, inaccessible using published reaction conditions.
共价有机框架（COFs）是一类经过广泛研究的多孔材料，它们在结晶度和高度模块化方面有别于其他多孔聚合物，因而具有广泛的应用。然而，用于合成稳定且结晶的COFs（如酰亚胺连接的COFs）的既定合成方案通常需要使用高沸点溶剂和有毒催化剂，这使得它们的合成成本高昂且对环境有害。在此，我们报告了一种新的环境友好策略——醇辅助水热聚合方法（aaHTP），用于合成多种结晶且多孔的酰亚胺连接的COFs。该方法使我们能够获得新型COFs，并通过用水和少量正醇替代常用有机溶剂混合物，最多可避免90%的有毒溶剂，且不受限于水溶性连接分子。此外，我们利用aaHTP通过连接取代展示了一种从亚胺连接的COF到新型酰亚胺连接的COF的生态友好型COF到COF的转化，这是已发表的反应条件无法实现的。
