Synthesis of crystalline g-C₃N₄ with rock/molten salts for efficient photocatalysis and piezocatalysis

Graphitic carbon nitride (g-C₃N₄) is emerging as a promising visible-light photocatalyst while the low crystallinity with sluggish charge separation/migration dynamics significantly restricts its practical applications. Currently, synthesizing highly crystalline g-C₃N₄ with sufficient surface activities still remains challenging. Herein, different from using alkali molten salts which is commonly reported, we propose an approach for synthesis of highly crystalline g-C₃N₄ with FeCl₃/KCl rock/molten mixed salts. The rock salt can serve as the structure-directing template while molten salt provides the required liquid medium for re-condensation. Intriguingly, the synthesized photocatalyst showed further enhanced crystallinity and improved surface area along with high π→π∗ excitation compared with crystalline C₃N₄ prepared from conventional molten-salt methods. These catalytically advantageous features lead to its superior photocatalytic and piezocatalytic activities with a high reactivity for overall water splitting that is not commonly reported for C₃N₄. This work provides an effective strategy for structural optimization of organic semiconductor based materials and may inspire new ideas for the design of advanced photocatalysts.