Copper Tuning the Reactivity of Bimetallic Cluster Anions Cu_nTa₂^- (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, Cu_nTa₂^- (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 Cu_nTa₂^- 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 Cu_nTa₂^- clusters and provides new insights into designing promising Cu-based bimetallic catalysts for methane conversion at low temperature.