Temperature-Tunable Selective Methane Catalysis on Au2

Low- (blue) and high- (red) temperature Au2+-catalyzed methane activation selective reaction cycles. Reaction kinetics and mass spectrometry radio frequency trap experiments in conjunction with first-principles density functional theory simulations reveal that gold dimer cations catalyze temperature-tuned selective reactions in gaseous mixtures of oxygen and methane. Temperature-controlled catalytic selectivity is demonstrated through the conversion of a mixture of methane and oxygen to formaldehyde at temperatures below 250 K (left catalytic cycle, blue color), while at higher temperatures (up to 300 K) dehydrogenation processes lead predominantly to formation of ethylene (right catalytic cycle, red color). On the bottom chart, we display the measured relative intensities of the catalyzed reaction products plotted versus the reaction temperature. Microscopic mechanisms were predicted theoretically and tested against the measured data. The corresponding molecular structures of the reaction intermediates and products are superimposed on the reaction cycles. Gold atoms are depicted by yellow spheres, oxygen atoms are in red, carbon atoms are in green, an