Rapid and Scalable Preparation of High-Crystalline Carboxyl-Functionalized Covalent Triazine Frameworks via Friedel-Crafts Reaction

Abstract

The Friedel-Crafts reaction has been extensively applied to the preparation of various porous organic polymers because of its simple operation and abundant building blocks. However, due to its poor reversibility and excessive random reactive sites, the synthesis of crystalline organic polymers/frameworks by Friedel-Crafts reaction has never been realized so far. Herein, we develop a molecular confined Friedel-Crafts reaction strategy to achieve rapid preparation (within only 30 minutes) of highly crystalline covalent triazine frameworks (CTFs) with tailorable functionality for the first time. Theoretical calculations and detailed experiments revealed the critical role of carboxyl groups in aromatic benzene monomer during the CTFs crystallization, which can not only effectively cause a suitable activation barrier for the electrophilic attack of 2,4,6-trichloro-1,3,5-triazine through their electron-withdrawing properties, but also introduce anchoring effects (molecular confinement effects) to facilitate the ordered polymerization at specific sites in 2D planar direction. Benefiting from the convenient synthetic route and low-cost raw materials, we could unprecedentedly realize the kilogram-scale fabrication of carboxyl-functionalized high-crystalline CTFs. Moreover, thanks to the hydrophilic and ionizable properties of carboxyl groups, the obtained functionalized CTFs exhibited excellent aqueous dispersibility and superior solution processability.