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

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-alpha-C-beta bond cleavage. The present work offers useful guidance for the design of efficient semiconductors for C-C bond cleavage through band structure engineering.