Selective oxidation of methane to light oxygenates under mild conditions remains challenging because thermal activation 

commonly leads to deep oxidation and carbon deposition. Here, a post-plasma catalysis (PPC) system integrating dielectric 

barrier discharge (DBD) plasma with Cu- and Ag-exchanged CHA-type zeolites, SAPO-34 and SSZ-13, enabled roomtemperature

conversion of methane to methanol and other oxygenates. Structural characterization confirmed that the CHA 

framework was largely preserved after metal exchange, with Cu species finely dispersed within the zeolite matrix, whereas 

Ag species were located mainly on the external surface. Under mild plasma conditions, CHA-based supports outperformed 

MFI- and BEA-type zeolites, giving higher selectivity toward oxygenates, including methanol and formaldehyde, together 

with lower coke formation, underscoring the role of zeolite confinement. Among the catalysts examined, Cu/SAPO-34 and 

Cu/SSZ-13 showed the best balance of methane conversion and oxygenate selectivity, and maintained performance over 

five consecutive short-term cycles. The introduction of Ag further shifted the product distribution from methanol toward 

formaldehyde. These findings identify Cu- and Ag-supported CHA zeolites as promising catalysts for energy-efficient 

plasma-assisted methane upgrading and highlight the combined importance of zeolite confinement and metal identity in 

governing oxygenate distribution.