Molecular doping of orthorhombic carbon nitride for efficient and selective photocatalytic biomass conversion

Advanced metal-free carbon nitride has critically needed towards a sustainable technique of photocatalytic conversion of biomass (PCB) into value-added chemicals. However, polymeric carbon nitride with amorphous structure usually faces challenges, such as low photogenerated charge carrier (electron/hole) separation, and poor photocatalytic activity and selectivity. Here, an orthorhombic carbon nitride has been developed with molecular site-doped melon to realize efficient PCB under light. A 2,1,3-benzothiazole-4,7-dicarbonitrile (BTDN) molecule has been doped into melon-chain to tailor the electronic structure and active site in orthorhombic carbon nitride (BTDN-u-Melon) for photocatalytic selective conversion of 5-hydroxymethylfurfural (HMF) and 2-phenoxy-1-phenylethanol (PPol). BTDN-u-Melon demonstrates remarkable performance in the photocatalytic conversion of HMF and PPol. For HMF, it achieves 81% conversion with 97% selectivity, representing a 6.75-fold enhancement in activity and a 1.4-fold improvement in selectivity over u-Melon. For PPol, it attains a 65.9% yield of benzaldehyde, with a significant improvement in catalytic performance. Mechanistic studies reveal the critical role of reactive oxygen species (˙O 2 - and 1 O 2 ) in the selective oxidation of HMF to 2,5-diformylfuran (DFF). This work provides valuable insights into the design and preparation of an approach for regulating the molecular chain structure of orthorhombic carbon nitride, paving the way for efficient visible-light photocatalytic molecular conversion.