Photoredox-Promoted Co-Production of Dihydroisoquinoline and H 2 O 2 over Defective Zn 3 In 2 S 6 .

One of the most sustainable and promising approaches for hydrogen peroxide (H 2 O 2 ) production in a low-cost and environment-friendly way is photosynthesis, which, however, suffers from poor carrier utilization and low H 2 O 2 productivity. The addition of proton donors such as isopropanol or ethanol can increase H 2 O 2 production, which, unfortunately, will inevitably elevate the entire cost while wasting the oxidizing power of holes (h + ). Herein, the tetrahydroisoquinolines (THIQs) is employed as a distinctive proton donor for the thermodynamically feasible and selective semi-dehydrogenation reaction to highly valuable dihydroisoquinolines (DHIQs), and meanwhile, to couple with and promote H 2 O 2 generation in one photoredox reaction under the photocatalysis by dual-functional Zn 3 In 2 S 6 photocatalyst. Surprisingly, the suitably defective Zn 3 In 2 S 6 offers an excellent and near-stoichiometric co-production performance of H 2 O 2 and DHIQs at unprecedentedly high rates of 66.4 and 62.1 mmol h -1 g -1 under visible light (λ ≥ 400 nm), respectively, which outperforms all the previously available reports even though sacrificial agents were employed in those reports. Additionally, photocatalytic redox reaction mechanism demonstrates that H 2 O 2 can be generated through multiple pathways, highlighting the synergistic effect among ROS (·O 2 - and 1 O 2 ), h + and proton donor, which has been ignored in previous studies.