Dissolution of g‐C3N4 Using Zinc Chloride Molten Salt Hydrates for Nanobelt Fabrication and Photocatalytic H2O2 Production

Graphitic-carbon nitride (g-C₃N₄), a metal-free two-dimensional layered semiconductor material, holds great potential for energy conversion, environmental remediation, and sensing. However, the limited solubility of g-C₃N₄ in conventional solvents hinders its widespread application. Improving the dissolution of g-C₃N₄ in the liquid phase is highly desired but challenging. Herein, we report an innovative approach to dissolve g-C₃N₄ using ZnCl₂ molten salt hydrates. The solubility of g-C₃N₄ in the solution reaches up to 200 mg mL^-1. Density functional theory (DFT) results suggest that ZnCl⁺H₂O is the key species that leads to charge redistribution on g-C₃N₄ surface and promotes the dissolution of carbon nitride in the solution. Furthermore, through dilution, the dissolved carbon nitride can be effectively recovered while maintaining its intrinsic chemical structure. The resultant regenerated C₃N₄ (r-C₃N₄) exhibits nanobelt morphology and demonstrates a substantially improved photocatalytic activity in H₂O₂ production. The rate of H₂O₂ production over the r-C₃N₄ reaches 20,228 μmol g^-1 h^-1, which is 6.2 times higher than that of pristine g-C₃N₄. This green and efficient dissolution route of g-C₃N₄ offers an effective approach for its diverse applications.