Rapid solid-phase synthesis of highly crystalline covalent organic framework platelets

Abstract

Covalent organic frameworks (COFs) have demonstrated superior performance in wide-ranging applications, yet their practical deployment has been long hindered by their inconvenient synthesis protocols. Toxic solvents, tedious procedures and long reaction times are typically involved in their synthesis, and microcrystalline powders are commonly obtained, which are unfavorable in practical use. Unfortunately, newly developed methods aiming to resolve these challenges often lead to deteriorated COF crystallinity and porosity. Here we develop a solid-phase hot-pressing method to fabricate 15 types of highly crystalline COF platelet of various linkage types, including imine-, hydrazone-, β-ketoenamine- and imide-linked COFs. Moreover, COF platelets with complex chemical structures, including a COF with three-dimensional geometry and a COF with multiple monomer components, have been successfully obtained. In particular, all COF platelets can be obtained within a short processing time of 0.5–5 min, with high crystallinity and porosity. Finally, as a proof-of-concept application, a β-ketoenamine-linked COF platelet is directly assembled into an atmospheric water harvesting device, demonstrating excellent water collecting performance. A solid-phase hot-pressing method is introduced, which can rapidly produce highly crystalline covalent organic framework platelets in a convenient, solvent-free manner. Fifteen platelets of various linkage types are produced, with a proof-of-concept demonstration of the resulting high-performing platelet type in an atmospheric water harvesting device.