Sequential Oxidation/Cyclization of Readily Available Imine Linkages to Access Benzoxazole‐Linked Covalent Organic Frameworks

• Published in: Angewandte Chemie 2024-03, Vol.136 (11), p.n/a
• Main Authors: Zhu, Yanqiu, Huang, Dekang, Wang, Wanqin, Liu, Gang, Ding, Chizhu, Xiang, Yonggang
• Format: Article
• Language: English
• Subjects: Amines; benzoxazole links; Covalent organic frameworks; generality; Oxidation; post-synthetic modifications
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202319909

Benzoxazole‐linked covalent organic frameworks (BO−COFs), despite their exceptional chemical stability, are still in their infancy. This is primarily because the current prevalent methods require the use of special ortho‐hydroxyl‐substituted aromatic amines as monomers. Herein, we report an innovative strategy to access BO−COFs directly from imine‐linked COFs (Im−COFs) without pre‐embedded OH groups, using a two‐step sequential oxidation/cyclization process. The two‐step process included the oxidation of Im−COFs into amide‐linked COFs, followed by a copper‐catalyzed oxidative cyclization. Five representative BO−COFs were synthesized with retained crystallinity and high oxidization efficiency, offering the potential to convert a significant portion of Im−COFs into BO−COFs. The structural advantages of the newly designed BO−COFs were demonstrated through their application to photocatalytic organic transformations. Benzoxazole‐linked COFs were synthesized through the two‐step sequential oxidation of readily available imine‐linked COFs, eliminating the requirement for a predesigned OH. This innovative method has high conversion efficiency, crystallinity preservation, and broad applicability, marking a significant advancement in expanding the library of benzoxazole‐linked COFs.