Z-Scheme heterojunction formation between CsPbBr3and BiOBr: key to singlet oxygen formation for selective semidehydrogenation of tetrahydroisoquinoline

Herein, a Z-scheme heterojunction has been constructed using BiOBr nanosheets (NSs) and CsPbBr3 quantum dots (QDs) for the selective semidehydrogenation of 1,2,3,4-tetrahydroisoquinoline (THIQ) to 3,4-dihydroisoquinoline (DHIQ). The interfacial internal electric field directs the photogenerated electron transfer from the conduction band (CB) of BiOBr to the valence band (VB) of CsPbBr3, resulting in an effective separation and transport of photogenerated charges. Furthermore, the heterojunction photocatalyst facilitates the activation of triplet oxygen to singlet oxygen. The optimized amount of CsPbBr3 QDs (20 wt%) loaded on BiOBr NSs (Z-20) achieved 97% yield of DHIQ by the selective semidehydrogenation process. The appropriate band alignment in Z-20 ensures two-electron selectivity for the semidehydrogenation of THIQ in contrast to other heterojunctions, constructed by the combination of different photocatalysts. Transient absorption spectroscopy reveals optimized exciton behavior in Z-20, characterized by fast internal relaxation and trapping, which affects the catalytic efficiency. This journal is © The Royal Society of Chemistry, 2025