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

Abstract

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 O2 under blue light irradiation. Furthermore, the facile adsorption sites of O2 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.