Atomically Dispersed WN₃O Sites on Defective Graphitic Carbon Nitride Enabling Efficient and Selective Photocatalytic...

Lignin valorization still is challenging of efficient and selective production of highly-functionalized aromatic compounds. Here atomically dispersed WN₃O sites on defective g-C₃N₄ (W₁/C_V-OCN) are fabricated by an in situ route, in which WN₃O sites are stabilized on C_V-OCN through reinforcing W─N (O) coordination interactions. The W₁/C_V-OCN exhibit excellent photocatalytic oxidation activity and selectivity in the depolymerization of lignin models and larch lignin. Under the conditions of 25°C, O₂ atmosphere and simulated sunlight irradiation, the optimal 0.96%W₁/C_V-OCN catalyst shows nearly complete conversion of a wide range of β-O-4 and β-1 lignin models, alongside more than 90% of C_α─C_β bond cleavage selectivity; particularly, the depolymerization of larch lignin is achieved over 0.96%W₁/C_V-OCN, affording 8.4% of benzaldehyde and 24.7% of guaiacol as the main products after 4 h light irradiation. Reaction mechanism studies reveal that single WN₃O sites not only facilitate lignin activation through photoinduced O-to-W charge transfer to produce alkoxy radical intermediates but also accelerate charge separation and transfer dynamics through directional electron transfer along W─N (O) bonds and dynamic transformation of W⁶⁺/W⁵⁺ states to ensure the formation of plentiful reactive oxygen species (ROSs). Precise β-scission (C_α─C_β and/or C_β─O bonds breakage) is achieved by synergy of alkoxy radical intermediates and ROSs.