Modifiable diyne-based covalent organic framework: a versatile platform for in situ multipurpose functionalization

Recently, research into functional materials with various desired properties has been ceaselessly promoted. However, the development of convenient and practical strategies for building flexible material platforms to realize multi-functionalization and to prepare various functional derivatives is still a challenge. Herein, we propose for the first time a new strategy that introduces conjugated carbon-carbon triple bonds into the skeleton of covalent organic frameworks (COFs) that can act as both building blocks and active sites to create a versatile platform. Based on the platform, in situ multipurpose functionalization according to diverse real needs can be achieved more easily and efficiently with different addition reactions, compared with current approaches used for the preparation of functional materials. In this paper, a novel COF material (TCD), which contains diynes acting as a skeleton of the material platform, was directly prepared under microwave irradiation. Then, three new functional materials with a cyano group (TCD-CN), an amidoxime group (TCD-AO) and a hydroxyl group (TCD-OH) were obtained by further functionalization of the C equivalent to C bonds in TCD. The capabilities of the prepared materials for the selective separation of uranium from a simulated nuclear industrial effluent were examined, and TCD-AO was found to exhibit the highest separation efficiency.