Room-Temperature Synthesis of Covalent Organic Frameworks using Gamma-Irradiation in Open-Air Conditions.

Abstract

Covalent organic frameworks (COFs), which have layered stacking structures, extended π-conjugation, and periodic frameworks have become a promising class of materials for a wide range of applications. However, their synthetic pathways frequently need high temperatures, enclosed systems under high pressures, an inert atmosphere, and extended reaction time, which restrict their practicality in real-world applications. Herein, the use of gamma irradiation is presented to synthesize highly crystalline COFs at room temperature under an open-air condition within a short time. This is demonstrated that there is no significant difference in crystallinity of COFs by gamma irradiation under air, N2 or Ar atmosphere conditions. Moreover, this approach can successfully fabricate COFs in the vessel with different degrees of transparency or even in a plastic container. Importantly, this strategy is applicable not only to imine linkage of COFs but also effective to the imide linkages of COFs. Most importantly, these COFs demonstrate improved crystallinity, surface area, and thermal stability in comparison to the corresponding materials synthesized via the solvothermal method. Finally, a COF synthesized through gamma irradiation exhibits remarkable photocatalytic activity in promoting the sacrificial hydrogen evolution from water, displaying a more catalytic efficiency compared with that of its solvothermal analogue.