Surfactant-free synthesis of covalent organic framework nanospheres in water at room temperature

Covalent organic frameworks (COFs) are a new class of porous materials receiving much attention due to their unique characteristics. However, COFs have been usually synthesized under harsh and complicated conditions, limiting their practical applications. We propose a surfactant-free strategy to controllably synthesize an imine-based covalent organic framework (COF) nanomaterial in water at room temperature. Introduction of tiny amounts of co-solvents not only achieves the morphology and size control of COFs but also ensures stability of COF nanomaterials in aqueous solution. Moreover, water as a solvent plays an important role in the size adjustment of COFs. The surface area of the obtained COFs was approximately 398 m2/g with a pore size distribution of about 2.8 nm. In addition, the COFs displayed a good crystallinity.