Unbiased Reaction Network Exploration of C-C Coupling in Methane Dehydroaromatization Over Mo-ZSM-5

Methane dehydroaromatization (MDA) over Mo-ZSM-5 zeolite catalysts is a promising route for the direct conversion of methane into valuable aromatic hydrocarbons. However, catalyst deactivation caused by coke formation remains a major challenge, and the underlying mechanisms are not fully understood. In this study, we applied automated reaction route mapping combined with rate constant matrix contraction (RCMC) to systematically explore reaction networks originating from methane molecules over two plausible active sites, [MoC]²⁺ and [Mo₂C₂]²⁺, confined within ZSM-5 zeolite. Without assuming predefined reaction products, the mapping revealed distinct reaction pathways and energetics for each active site. Over [MoC]²⁺, C₂H₄ was identified as a key intermediate with a relatively low desorption energy. In contrast, [Mo₂C₂]²⁺ facilitated the formation of C₃ and C₄ species with high desorption energies. Importantly, the regeneration of [MoC]²⁺ from methane alone was not observed, whereas CO promoted regeneration, consistent with experimental reports of CO-assisted catalyst stability. These findings provide detailed mechanistic insight into hydrocarbon formation and catalyst deactivation and highlight the utility of automated reaction mapping in rational catalyst design.