Construction of triazine-heptazine-based carbon nitride heterojunctions boosts the selective photocatalytic C−C bond cleavage of lignin models

• Published in: Applied catalysis. B, Environmental Environmental, 2023-08, Vol.331, p.122688, Article 122688
• Main Authors: Zhang, Qingqing, Chu, Yi-Chun, Liu, Zhulan, Hong, Mei, Fang, Weiwei, Wu, Xin-Ping, Gong, Xue-Qing, Chen, Zupeng
• Format: Article
• Language: English
• Subjects: Crystalline carbon nitride; C−C bond cleavage; Lignin valorization; Photocatalysis; Triazine-heptazine heterojunctions
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2023.122688

Photocatalytic lignin depolymerization emerges as a sustainable and cost-competitive strategy to produce low-molecular-weight aromatic chemicals from renewable resources. Significant efforts have been devoted to engineering C−C bond cleavage photocatalysts with diverse compositional and morphologic characteristics in the past decade. We herein present a facile photocatalytic strategy of promoting C−C bond cleavage in lignin models to achieve high-yield aromatic monomers over triazine-heptazine-based carbon nitride heterojunctions, exceeding the triazine- or heptazine-based counterparts. Mechanistic investigations reveal that the photo-excited electron and hole synergistically trigger the C−C bond cleavage. A combination of experimental results and theoretical calculations confirms that the improved photocatalytic performance is primarily attributed to the accelerated charge carriers separation and migration induced by the built-in electric field at the heterojunction interface, and the facilitated Cβ-radical generation. These findings highlight the effectiveness of interfacial engineering of intramolecular heterostructures towards the rational promotion of photocatalytic cleavage of C−C bond in lignin models. [Display omitted] •Carbon nitride heterojunctions are synthesized via NaCl/KCl-induced polymerization.•High selectivity of photocatalytic C−C bond cleavage in lignin models is achieved.•Excellent-yield for aromatic monomers is achieved over carbon nitride heterojunctions.•The photo-excited electron and hole synergistically trigger the C−C bond cleavage.•Carbon nitride heterojunctions accelerate electron-hole separation and migration.