Photocatalytic aerobic thiocyanation/sulfonylation of alkynes by D-A type COFs: Enhanced generation of superoxide and sulfur-based radicals via building units adjusted band structures.

[Display omitted] • Well-tuned band structure and redox ability by adjusting electron D-A capacity of building units. • Selective thiocyanate/sulfonyl radicals generation by h+ oxidation. • Reactive oxygen species production by photogenerated e− reduction. • Tandem sulfur-based radical addition/vinyl radical coupling with ROS/enol tautomerism. • No electron sacrificial agents or extra additives as precursor of singe electron transfer reagents. Photocatalytic radical-mediated aerobic thiocyanation/sulfonylation of alkynes represents the most straightforward and atom-economic method to synthesize α-thiocyanate/sulfonyl ketones. The core issue is the generation of desired thiocyanate/sulfonyl radicals and their subsequent conversion into target products. In this work, three polyimide-based donor–acceptor COFs, named TAPB-PMDA, TTA-PMDA, and TTA-NDA, respectively, have been prepared for the photosynthesis of α-thiocyanate/sulfonyl ketones. Based on efficient adjusting electron donor-accept capacity of building units, TTA-NDA possesses broader visible absorption, richer redox properties, faster carrier separation efficiency and shows higher photocatalytic activity in thiocyanation/sulfonylation of alkynes under blue LED light illumination. Control experiments and EPR tests provide insight into the tandem radical addition/cross-coupling mechanism, in which the thiocyanate/sulfonyl radicals generation via h+ oxidation and the reactive oxygen species (ROS, e.g. •OH, H 2 O 2 , 1O 2 , O 2 •−) production by e− reduction carry out simultaneously, avoiding the employing of electron sacrificial agents or extra additives as precursors of singe electron transfer reagents. This operable strategy opens up a door for the difunctionalization of alkynes in photosynthetic manner. [ABSTRACT FROM AUTHOR]