Unveiling the Catalytic Mechanism and Selectivity Control Strategies of Two-Dimensional C ₃ N Materials for Propane Oxidative Dehydrogenation: A DFT Study

Propane oxidative dehydrogenation (PODH) is recognized as a promising route for the production of propylene. However, developing highly active and selective catalysts for the on-purpose synthesis of propylene remains a substantial challenge. Recent reports suggest that carbon–nitrogen materials with uniformly dispersed nitrogen species can significantly increase the propylene yields in catalytic PODH reactions. Herein, the density functional theory methods are employed to explore the catalytic mechanism and performance for PODH on C3N material. The results of the initial dehydrogenation reaction intermediates and potential barriers demonstrate that the dehydrogenation of propane on C3N follows a radical mechanism where the first C–H bond activation is the rate-limiting step. The detailed reaction pathway and catalytic selectivity are meticulously unveiled. It is revealed that isopropyl radicals preferentially form propylene rather than other products. The microkinetic model analysis identifies that the N vacancies and edge sites play crucial roles in the catalytic selectivity. Under conditions of 775 K with a propane conversion rate of 13.0%, these sites exhibited remarkable selectivity (up to 65.1%) compared to the C–O groups of a perfect C3N surface (0%). Furthermore, during the active regeneration of surface sites, a competitive relationship exists between the two reaction pathways: 2OH* → H2O* + O* and 2OH* + O2* → H2O2* + 2O*. Therefore, controlling lower oxygen partial pressure or a higher concentration of N vacancies is key to ensuring the catalytic selectivity of C3N. Based on these results, we provide a detailed description of the catalytic performance of PODH on the C3N catalyst, laying a foundation for future optimization.