A facile solution-phase synthetic approach for phenol-based porous organic cages and covalent organic frameworks
Porous crystalline materials, such as porous organic cages (POCs) and covalent organic frameworks (COFs), are important in a wide range of applications such as gas storage/separation, sensing and catalysis. The conventional synthetic approach for imine-based POCs and COFs usually involves the use of organic solvents/acid catalysts (such as AcOH or TFA). However, synthesizing and growing POCs crystals and COFs crystallites with enhanced crystallinity are not an easy-to-perform process, in which many reaction parameters need to be screened. To overcome these problems, we have proposed herein a facile and green synthetic strategy by adopting H2O/organic solvent/MOH (M = Na, K, Cs) as the reaction media to produce a series of phenol-based POCs and COFs. X-ray crystallography and molecular simulations have been used to confirm their structures in addition to NMR, mass and FT-IR spectra, and gas sorption experiments reveal their porosity and sorption property. This new approach provides not only an efficient and alternative way to synthesize high crystalline POCs and even COFs but also an insight into the crystallization process of these two kinds of porous materials especially in the hydrous media.