Iron-containing zeolite catalysts (Fe-zeolites) demonstrate exceptional performance in selective oxidation of methane to C₁ oxygenates, while aerobic C–C coupling to C₂ hydrocarbons has remained elusive. The heterogeneity of Fe species within zeolites, intertwined with kinetically competing over-oxidation processes, engenders ambiguities in determining catalytic pathways, thereby fundamentally impeding rational design of the catalyst. Here, we report that continuous aerobic C–C coupling of methane can be achieved under oxygen-lean conditions over tailored Fe-zeolites. Crucially, the oxygen-lean environment enables clear identification of distinct active-site roles: CO is directly generated on low-coordinated monomeric Fe sites, while C₂ hydrocarbons formation predominantly occurs on coordinatively saturated monomeric Fe sites. Detailed spectroscopic studies and density functional theory (DFT) calculation reveals that steric effect of octahedral-coordinated monomeric Fe³⁺ Lewis acid sites (LAS) compels *CH₃ species to preferentially bind to the Brønsted acid sites (BAS), facilitating C–C coupling and suppressing overoxidation. Furthermore, the Mars–van Krevelen (MvK) mechanism is verified as a feasible pathway for methane-to-ethane conversion. This work elucidates the critical role of Fe site coordination in dictating reaction pathways during oxygen-mediated methane conversion.

Efficient industrial hydrogen production via water splitting hinges on the development of highly effective oxygen evolution catalysts and a clear understanding of their catalytic mechanisms. Among various strategies, exploiting the synergistic effects of transition metals has shown great promise, although the underlying mechanisms remain elusive. Here, we investigate bi-transition metal borides, Mo₂MB₂ (M = Co and Ni), as a model system to unravel these synergistic effects and the evolution of active species during the oxygen evolution reaction (OER). Using combined in-situ and ex-situ characterization techniques, we monitor the structural and valence changes of constituent elements in real time. We find that Mo and B undergo oxidation and dissolution at the anode, initiating distinct evolutionary pathways. In Mo₂CoB₂, rapid structural collapse leads to the formation of γ-CoOOH as the active species. In contrast, Mo₂NiB₂ exhibits a more gradual surface-driven transformation, producing γ-NiOOH and Ni–O–Mo species. Chronopotentiometry testing reveals continued Mo and B dissolution, culminating in the transition of γ-phases to amorphous states, followed by recrystallization into β-phases. This study provides critical insights into dissolution-induced structural evolution, active species dynamics, and the synergistic interactions between Mo/B and Co/Ni during OER catalysis.