Synergistic three-in-one photo-synthesis of benzimidazoles and H2O2 by porous N-rich g-C3N4/g-C3N5 isotype heterojunction

Constructing a dual-functional photoredox system coupling fine-chemical synthesis with hydrogen peroxide (H 2 O 2 ) production provides an intriguing and eco-friendly protocol for advancing sustainable practical applications. Herein, we present a facile one-pot strategy for fabricating a porous N-rich g-C 3 N 4 /g-C 3 N 5 heterojunction (denoted as pN-N 4 -N 5 ) using mixed melamine and 3-amino-1,2,4-triazine as the precursors with NH 4 Cl as a penetrant for in-situ structure engineering. The resultant metal-free pN-N 4 -N 5 exhibited a remarkable performance of H 2 O 2 generation rate of 2.71 mmol g −1 h −1 with simultaneous production of industrially important 2-phenylbenzimidazole (2-BZ) under visible light and open air, along with a yield of 97 % and selectivity of > 99 %, outperforming most of the reported carbon nitride-based reaction systems for single-functional H 2 O 2 or 2-BZ synthesis. Extensive characterizations and density functional theory (DFT) studies revealed that such a heterojunction with well-matched band structure, enlarged interlayer space and enriched amino groups on the catalyst surface enables the facilitated spatially oriented charge flow, efficient mass transfer and reactants activation, thus offering an efficient and sustainable platform to furnishing the three-in-one photoredox systems to produce bidirectional valuable products.