Designed synthesis of large-pore crystalline polyimide covalent organic frameworks

Covalent organic frameworks (COFs) are an emerging class of porous crystalline polymers with a wide variety of applications. They are currently synthesized through only a few chemical reactions, limiting the access and exploitation of new structures and properties. Here we report that the imidization reaction can be used to prepare a series of polyimide (PI) COFs with pore size as large as 42 × 53 Å2, which is among the largest reported to date, and surface area as high as 2,346 m2 g−1, which exceeds that of all amorphous porous PIs and is among the highest reported for two-dimensional COFs. These PI COFs are thermally stable up to 530 °C. We also assemble a large dye molecule into a COF that shows sensitive temperature-dependent luminescent properties. Covalent organic frameworks are a potentially useful class of materials, although they are currently synthesized using relatively few reactions. Here, the authors show that the imidization reaction can be used to prepare a series of large pore polyimide frameworks with high surface area and thermal stability.