Titanium nitride@nitrogen-enriched porous carbon derived from metal–organic frameworks and melamine: A remarkable oxidative catalyst to remove indoles from fuel

Titanium nitride (TiN) catalysts, supported on nitrogen-enriched carbon, were prepared via carbonization of a Ti-based metal–organic framework (MOF)/melamine mixture. The prepared catalysts were applied first to the oxidation of indoles as a potential catalyst and showed remarkable performance in oxidative denitrogenation (ODN) of fuel. For example, a developed catalyst, TiN@CN-2, has a high turnover frequency (58.1 h⁻¹), the lowest activation energy (31.0 kJ∙mol⁻¹), and reusable catalytic performance, rendering it a competitive catalyst for ODN. Based on experimental studies (scavenger and electron spin resonance) and theoretical calculations, remarkable performance of TiN@CN-2 in ODN could be attributed to a nonradical mechanism involving active Ti-peroxo species. Additionally, compared with titanium oxides, titanium nitrides have a higher efficiency in H₂O₂ activation and the formation of Ti-peroxo species. Therefore, TiN, particularly when supported on nitrogen-enriched carbon (such as TiN@CN), could be proposed as a potential catalyst for oxidation reactions, including ODN. Finally, this work will pave the way for both a new oxidation catalyst and a facile synthesis of metal nitrides.