Boosting photocatalytic benzylic C(sp³)-H bonds oxidation via an embedded S-scheme BA₂PbBr₄/MoO₃ heterojunction

The selective oxidation of benzylic C(sp³)-H bonds to aldehydes/ketones is pivotal in production of value-added chemicals, but remains challenging to proceed under moderate conditions with high production rate. Semiconductor photocatalysis offers a sustainable alternative by utilizing solar energy and O₂, yet catalysts face limitations due to fast charge recombination and insufficient surface reactivity. Here, we develop a novel S-scheme heterojunction of BA₂PbBr₄/MoO₃ by integrating MoO₃ nanobelts into BA₂PbBr₄ nanoplates to form an embedded architecture. The design forms a tight and large interfacial contact and establishes a built-in electric field (BEF) at interfaces, providing sufficient charge transfer channels to direct charge separation while preserving strong redox potentials. Importantly, MoO₃ enhances toluene adsorption, enriching reactants on the catalyst surface and accelerating mass/charge transfer. The optimal BA₂PbBr₄/MoO₃ heterojunction achieves 5560 μmol g^-1 h^-1 and 880 μmol g^-1 h^-1 for benzaldehyde and benzyl alcohol production, respectively, which are 2.5-fold higher than pure BA₂PbBr₄. This study highlights S-scheme heterojunction engineering as a strategic approach to enhance photocatalytic performance by synergizing charge dynamics and surface reactivity, offering a green pathway for selective CH bond functionalization in chemical synthesis.