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.