Inserting acetylene into an olefin-linked covalent organic framework for boosting the selective photocatalytic aerobic oxidation of sulfides

Covalent organic frameworks (COFs) with superior semiconducting properties imparted by sufficient pi-conjugations and ordered structures have great potential in visible light photocatalysis. Thus, introducing extra pi-conjugated rigid units into the olefin-linked COFs is effective to promote charge transfer and performance. Here, two olefin-linked COFs, TBP-COF and TBPA-COF, were synthesized by reacting 2,4,6-trimethyl-1,3,5-triazine (TMT) with 4,4'-bis(formyl)biphenyl (BFP) and bis(4-formylphenyl)acetylene (BFPA) through organic acid-induced solvothermal condensation. Both TBP-COF and TBPA-COF microspheres were with high crystallinity and uniform micropores. Owing to the insertion of acetylene, TBPA-COF possessed an extended pi-conjugated structure that is conducive to smooth charge transfer. Compared to TBP-COF, TBPA-COF delivered superior photocatalytic performance on the selective aerobic oxidation of organic sulfides. Besides, both electron and energy transfer pathways contributed to the formation of sulfoxides over TBPA-COF. This work presents the ascendancy of inserting acetylene into olefin-linked COFs in building efficient visible light photocatalysts for organic oxidations.