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

Abstract

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.