Achieving productive aerobic oxidation of alcohols in the presence of more easily oxidized partners is a central challenge in photocatalytic synthesis. In particular, visible-light-driven routes from abundant primary alcohols to benzimidazoles are hampered by the inertness of linear aliphatic alcohols and the oxidative fragility of o-phenylenediamines (OPDs), which has forced previous methods to use the alcohol as the bulk solvent. Here we show that halide-tuned CsPbX3 (X = Cl/Br/I) perovskite nanocrystals act as adsorption-biased, band-engineered photocatalysts for this transformation. By adjusting the halide composition, we prepare a toolbox of photocatalysts whose excited-state oxidation potentials are matched to different classes of primary alcohols: CsPbCl3 under 405 nm irradiation efficiently oxidizes linear aliphatic alcohols, whereas CsPbClBr2 under 455 nm light is optimal for benzylic alcohols. For challenging linear aliphatic alcohols, this oxidative dehydrogenative coupling operates with only ∼3 equiv of the alcohol (rather than solvent-level quantities), while benzylic alcohols are converted with only 2 equiv, in all cases using O2 (1 atm) as the terminal oxidant under mild, noble-metal-free and heterogeneous conditions to furnish a broad range of 2-alkyl and 2-aryl benzimidazoles. Temperature-programmed desorption experiments and density functional theory (DFT) calculations indicate that primary alcohols bind much more strongly to the perovskite surface than OPDs, while photophysical and electrochemical studies map a two-step interfacial electron-transfer sequence: alcohol → perovskite(h+) → O2. Together, these results demonstrate an adsorption-biased, halide-tunable perovskite platform for alcohol-favored aerobic oxidation and suggest a general design strategy for heterogeneous photoredox synthesis.
Lu et al. (2026) studied this question.