Recyclable Quasi-Homogeneous Carbon Nitride Colloidal Catalyst for Sustainable Photocatalytic H₂O₂ Generation

Graphitic carbon nitride (g-C₃N₄) photocatalysts have attracted growing interest for the eco-friendly, solar-driven synthesis of hydrogen peroxide (H₂O₂). However, the catalytic efficiency remains limited by poor accessibility of reactive sites due to the hydrophobic nature and aggregation tendency of conventional g-C₃N₄. Here, we report a hydrophilic g-C₃N₄ colloidal photocatalyst, synthesized via potassium ion (K⁺) incorporation and surface grafting with sulfonylcyanide groups, which enables quasi-homogeneous photocatalytic H₂O₂ production (7,886 µmol g⁻¹ h⁻¹), surpassing most reported g-C₃N₄-based heterogeneous systems. The sulfonylcyanide groups facilitate O₂ adsorption and reduction, while synergistically promoting charge separation in conjunction with K⁺ ions. This work demonstrates the potential of hydrophilic g-C₃N₄ colloids in quasi-homogeneous catalysis and presents a versatile strategy for designing advanced g-C₃N₄-based photocatalysts for sustainable chemical synthesis.