Z-Scheme heterojunction formation between CsPbBr3 and BiOBr: key to singlet oxygen formation for selective semidehydrogenation of tetrahydroisoquinoline

Abstract

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.