Lead-halide perovskite quantum dots embedded in mesoporous silica as heterogeneous photocatalysts combined with organocatalysts for asymmetric catalysis

Abstract

Asymmetric photocatalysis consists of the synergistic effect of photocatalysis and organocatalysis, in which the photoelectrons in photocatalysts catalyze substrates to produce free radical intermediates, and chiral substances can control the stereoscopicity. However, photocatalysts are mainly concentrated in noble-metal materials, and perovskites with excellent photoelectric properties are rarely applied in asymmetric catalysis, mainly due to their susceptibility to catalytic environments. Hence, we embedded CsPbBr₃ quantum dots into KIT-6 mesoporous silica to form silica-shell-protected heterogeneous photocatalysts (CsPbBr₃@KIT-6), which were further combined with chiral organocatalysts to explore the activity and stereoselectivity in asymmetric photocatalysis. The well-dispersed CsPbBr₃ in KIT-6 channels provides more active sites and exhibits excellent enantioselectivity in the formation of the C–C bond and cross-dehydrogenation coupling of C–H bonds (75.3–91.3% and 74.9–94.0%, respectively). Meanwhile, the turnover number (TON) of the 20CsPbBr₃@KIT-6 photocatalyst with 20 wt% of CsPbBr₃ reaches at least 36 700, which is 215 times higher than that of noble metal Ru photocatalysts in an N₂ atmosphere and 458 times higher in an air atmosphere.