Lighting the Way: Unveiling the Mechanisms of the Photoinduced Benzyl Alcohol Oxidation Using Tailored Bismuth‐Based Perovskite‐Inspired Microcrystals

This study reveals that a fine balance between experimental conditions and catalyst design enhances the visible-light-driven oxidative process of benzyl alcohol in air. A comparative analysis of various bismuth-based halide perovskite-like materials with differing chemical compositions uncovers that the Cs3Bi2Br9 material outperforms the others, owing to its optimal bandgap and well-aligned energy levels. Notably, small-sized Cs3Bi2Br9 particles prepared under halide-rich conditions promote the evolution of the benzaldehyde product with an unprecedented product evolution rate (14,525 μmol g−1 h−1), among the highest reported for heterogenous photocatalysis. The excess halide inhibits the particle growth and, being easily removed along with the bulky ammonium counterion by the washing steps after the synthesis, releases the metal catalytic sites at the surface responsible for the improved catalytic performances. Mechanistically, dehydrogenative (anyway leading to aldehydic products) and degradation pathways are found to be competitive with the substrate oxidation promoted by oxygen reactive species, while their individual contribution is correlated with the surface chemistry of the photocatalyst and is supported by theoretical calculations. Therefore, the insights of this study are considered fundamental for shining light on future chemical strategies for enriching the potential of perovskite materials toward sustainable transformations.