Pure Crystalline Covalent Organic Framework Aerogels

Covalent organic frameworks (COFs) are crystalline organic materials of interest for a wide range of applications due to their porosity, tunable architecture, and precise chemistry. However, COFs are typically produced in powder form and are difficult to process. Herein, we report a simple and versatile approach to fabricate macroscopic, crystalline COF gels and foams. Our method involved the use of dimethyl sulfoxide as a solvent and acetic acid as a catalyst to first produce a COF gel. The COF gel was then washed, dried, and reactivated to produce a macroscopic, crystalline, porous COF foam. We demonstrated this synthesis for six different imine COFs and found that the crystallinities and porosities of the COF foams matched those of COF powders. Electron microscopy revealed a robust hierarchical pore structure, and we showed that the COF foams can be used as absorbents in oil-water separations, for the removal of organic and inorganic micropollutants, and for the capture and retention of iodine. This study provides a versatile and simple approach for the fabrication of COF foams and will provide novel routes for incorporating COFs in applications that require macroscopic, porous materials.