Abstract: Pyrolysis of the Ta₂O₅/melamine mixture in molten chlorides is herein demonstrated as a facile and controllable method to nitridize and functionalize Ta₂O₅. The influence of the stoichiometry and composition of Ta₂O₅/melamine in molten salts on the nitridation process is rationalized to ensure the controllable preparation of Ta₃N₅ and Ta₃N₅/TaON. The characterization results, including scanning electron microscopy, transmission electron microscopy, elemental mapping, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy, all confirm the existence of the Ta₃N₅/TaON heterojunction, in which the TaON nanoparticles are closely anchored to the Ta₃N₅ nanorods. Benefiting from its composition and structure, the Ta₃N₅/TaON composites show enhanced photocatalytic activity for the degradation of methylene blue. The present study highlights that the molten salt method using a solid nitrogen source can be a new technique for rationalizing the design of nitrides and oxynitrides.