Thiazole-linked isomeric covalent organic frameworks for divergent photocatalysis: Selective oxidation of organic sulfides

The photocatalysis of covalent organic frameworks (COFs) is underpinned by their inherent structures in which the linkage plays a vital role in determining the activity. The transformation of imine into thiazole leads to isomeric structures owing to the different orientations of linkages. Here, two thiazole-linked COFs, COF-TZ-1 and COF-TZ-2, are constructed from two imine-linked COFs, COF-IM-1 and COF-IM-2, with the imine N next to the linker triphenylbenzene and triphenyltriazine, respectively. Despite better absorption, COF-TZ-1 possesses inferior optoelectronic properties to COF-TZ-2. Besides, the dipole moment of COF-TZ-2 is twice that of COF-TZ-1. COF-TZ-2 is much better than COF-TZ-1 for blue light photocatalytic selective oxidation of organic sulfides with O-2 under blue light irradiation. Furthermore, the facile adsorption sites of O-2 are verified by density functional theory calculations, and the generation of superoxide is tracked over COF-TZ-2. This work highlights that subtle variations of COFs can lead to divergent photocatalysis.