Unlocking the dual functions of MOFs: Phosphorus-doped carbon nitride modified Bi-MOF-derived bismuth oxide for photocatalytic cleavage of lignin Cα–Cβ bonds

Efficient and selective cleavage of C–C bonds in lignin remains a critical hurdle for its sustainable valorization into aromatic chemicals. Herein, we rationally construct a Z-scheme heterojunction photocatalyst by integrating phosphorus-doped graphitic carbon nitride (P-CN) with rod-like Bi 2 O 3 derived from a bismuth metal–organic framework (Bi-MOF). Phosphorus doping effectively modulates the band structure of g-C 3 N 4 , broadening visible-light absorption and enhancing its reduction capacity. Notably, Bi-MOF serves a dual function: it acts as the precursor for rod-like Bi 2 O 3 while simultaneously functioning as a pore-generating agent. Its decomposition during thermal treatment imparts substantial mesoporosity to the overlying g-C 3 N 4 nanosheets, dramatically increasing the specific surface area of the heterojunction. This mesoporous architecture and high surface area facilitate lignin diffusion and oxygen capture, thereby promoting the generation of carbon-centered radical intermediates and singlet oxygen—the key reactive species driving lignin C α –C β bond cleavage. Consequently, the optimized P-CN/Bi 2 O 3 catalyst achieves 97.5% conversion of the lignin model compound, 2-phenoxy-1-phenylethanol, and 94.3% benzaldehyde yield under 405 nm light irradiation, drastically outperforming pristine Bi 2 O 3 (31.4% conversion, 30.5% yield) and P-CN (55.8% conversion, 50.9% yield). This work highlights the untapped potential of MOF-derived materials in morphological engineering, offering new design principles for high-performance photocatalytic systems toward sustainable lignin valorization.