Z-Scheme nanocomposite with high redox ability for efficient cleavage of lignin C–C bonds under simulated solar light

Abstract

Depolymerization of lignin, a key component of lignocellulose, is a sustainable approach to provide value-added aromatics. Selective cleavage of recalcitrant C–C linkages is a key challenge for lignin depolymerization. Photocatalysis, which can provide highly reactive species under mild conditions, represents a potential strategy for such C–C bond cleavage. Here, we report an efficient approach to break lignin C–C bonds using a Z-scheme Ag₃PO₄−polymeric carbon nitride (PCN) nanocomposite under simulated solar light at room temperature. Various lignin model compounds were converted into aromatic aldehydes with high yields of 66%–95%. Our mechanistic study reveals that the C–C bond cleavage mainly involves an electron–hole coupled photoredox mechanism. The construction of a Z-scheme Ag₃PO₄–PCN heterojunction structure is essential to simultaneously preserve the strong reduction and oxidation capability of its components, which is key for the electron–hole coupled C_α–C_β bond cleavage. The present work offers useful guidance for the design of efficient semiconductors for C–C bond cleavage through band structure engineering.