Copper Tuning the Reactivity of Bimetallic Cluster Anions CunTa2– (n = 0–4) toward Methane

Activation of methane under mild conditions is a challenging subject due to its inherent chemical inertness. Metal doping has been proven to be an effective strategy to optimize the catalysts' performance for methane conversion; however, the detailed mechanism underlying doping to regulate the reactivity of the bimetallic active sites remains poorly understood at the strictly molecular level. Herein, the reactivity of atomically precise bimetallic cluster anions, CunTa2- (n = 0-4), toward methane has been investigated at room temperature by state-of-the-art mass spectrometry in conjunction with density functional theory calculations. Both Cu2Ta2- and Cu3Ta2- clusters could bring about methane dehydrogenation, whereas Ta2-, CuTa2-, and Cu4Ta2- are inert with CH4. Mechanistic studies reveal that variations in the number of Cu atoms within CunTa2- significantly alter the composition and energy levels of frontier orbitals, which in turn modulate the activity of the dinuclear Ta-Ta site toward activating the C-H bond. This study emphasizes the importance of appropriately doped Cu atoms in regulating the reactivity of CunTa2- clusters and provides new insights into designing promising Cu-based bimetallic catalysts for methane conversion at low temperature.