An sp² Carbon-Conjugated Benzotrithiophene Covalent Organic Framework toward Blue Light Photocatalysis

The wide tunability of covalent organic frameworks (COFs) enables them to be promising for visible light photocatalysis. Herein, the integration of the 2,2'-(benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diyl)diacetonitrile (BBT) linker and the benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarbaldehyde (BTT) knot yields an sp² carbon-conjugated COF, BBT-BTT-COF, with an ordered donor-acceptor architecture. Importantly, BBT-BTT-COF exhibits a crystalline framework, uniform porosity, high specific surface area, and broad visible light absorption. Optoelectronic characterizations disclose the effective charge separation and transfer of BBT-BTT-COF. Capitalizing on these merits, BBT-BTT-COF photocatalysis demonstrates high efficiency in the selective oxidation of thioanisoles under blue light irradiation, while also exhibiting excellent recyclability and a broad substrate scope. Mechanistic investigations identify the electron transfer to oxygen as the dominant pathway. This work highlights the critical role of rational design of the linkage of COFs in pushing the boundaries of photocatalysis toward diverse selective organic transformations.