Unveiling the Mechanism of Plasma-Catalyzed Oxidation of Methane to C 2+ Oxygenates over Cu/UiO-66-NH 2 .

Nonthermal plasma (NTP) offers the potential for converting CH 4 with CO 2 into liquid products under mild conditions, but controlling liquid selectivity and manipulating intermediate species remain significant challenges. Here, we demonstrate the effectiveness of the Cu/UiO-66-NH 2 catalyst in promising the conversion of CH 4 and CO 2 into oxygenates within a dielectric barrier discharge NTP reactor under ambient conditions. The 10% Cu/UiO-66-NH 2 catalyst achieved an impressive 53.4% overall liquid selectivity, with C 2+ oxygenates accounting for ∼60.8% of the total liquid products. In situ plasma-coupled Fourier-transform infrared spectroscopy (FTIR) suggests that Cu facilitates the cleavage of surface adsorbed COOH species (*COOH), generating *CO and enabling its migration to the surface of Cu particles. This surface-bound *CO then undergoes C-C coupling and hydrogenation, leading to ethanol production. Further analysis using CO diffuse reflection FTIR and 1 H nuclear magnetic resonance spectroscopy indicates that in situ generated surface *CO is more effective than gas-phase CO (g) in promoting C-C coupling and C 2+ liquid formation. This work provides valuable mechanistic insights into C-C coupling and C 2+ liquid production during plasma-catalytic CO 2 oxidation of CH 4 under ambient conditions. These findings hold broader implications for the rational design of more efficient catalysts for this reaction, paving the way for advancements in sustainable fuel and chemical production.