Halogen–Hydrogen Bonding for the Synthesis of Efficient Polymeric Carbon-Nitride Photocatalysts

Carbon nitride (CN) materials demonstrate great promise as photocatalysts for various reactions. However, synthesizing a CN with high dispersibility in water, large specific surface area, ordered morphology, and high catalytic activity remains a challenge. Melem (2,5,8-triamino-tri-s-triazine) has emerged as a monomer for the synthesis of CN materials owing to its high thermal stability, which favors controlled condensation over sublimation and decomposition at high temperatures. Herein, the synthesis of porous CN materials is shown with high dispersibility in water and excellent photocatalytic activity for the hydrogen evolution reaction (HER). To this end, various supramolecular assemblies are designed which are composed of melem combined with different hydrohalogenic acids as precursors of CNs. The results show that the HX (HX (aq), where X = Cl, Br, I) type directs the morphology, optical, and electronic properties of the resulting CN materials, particularly their surface area and photophysical properties. Moreover, the presence of HX results in a CN with a larger amount of free NH₂ groups, which allow good dispersibility in water and act as linking groups to a photodeposited Pt cocatalyst. The elucidation of the optimum acid concentration and type leads to the synthesis of a CN with high and stable photocatalytic HER activity.