Boosted photocatalytic oxidation of benzylic C(sp3)-H bonds over C3N4/PMA2PbBr4 via synergistic promotion of charge separation and substrate adsorption

Photocatalytic selective oxidation of benzylic C( sp 3 )-H bonds to high-value oxygenates holds great potential for sustainable organic synthesis, yet remains challenging due to inefficient charge separation and limited substrate activation over conventional photocatalysts. Herein, a C 3 N 4 /PMA 2 PbBr 4 heterojunction is rationally designed via an anti-solvent strategy, integrating 2D PMA 2 PbBr 4 with π-conjugated C 3 N 4 . Experimental and theoretical analyses reveal that the internal electric field induced by band alignment drives spatial charge separation, preserving the powerful holes in the valence band of PMA 2 PbBr 4 for direct C H bond activation and electrons in the conduction band of C 3 N 4 for efficient O 2 reduction. Notably, C 3 N 4 demonstrates enhanced toluene adsorption via π-π interactions, concentrating substrates at reactive interfaces. The synergistic interplay of optimized charge dynamics and molecules activation enhances hole-mediated C H cleavage and radical-driven further oxidation. Consequently, the optimized 5 % C 3 N 4 /PMA 2 PbBr 4 achieves a benzaldehyde production rate of 5783 μmol g −1  h −1 under visible light, outperforming pristine PMA 2 PbBr 4 by a factor of 1.7 and C 3 N 4 of 25.8.