A theoretical study on doping Pd-like superatoms into defective graphene quantum dots: an efficient strategy to design single superatom catalysts for the Suzuki reaction

The rational design of non-precious metal catalysts as a replacement for Pd is of great importance for catalyzing various important chemical reactions. To realize this purpose, the palladium-like superatom NbN was doped into a defective graphene quantum dot (GQD) model with a double-vacancy site to design a novel single superatom catalyst, namely, NbN@GQD, based on density functional theory (DFT), and its catalytic activity for the Suzuki reaction was theoretically investigated. Our results reveal that this designed catalyst exhibits satisfactory activity with a small rate-limiting energy barrier of 25.7 kcal mol^-1, which is comparable to that (22.8 kcal mol^-1) of the commonly used Pd(PPh₃)₂ catalyst. In addition, the size and substituent effects of the GQD support on the catalytic activity of NbN@GQDs were systematically studied. It is found that increasing the GQD size slightly reduced the rate-limiting energy barrier to 24.1 kcal mol^-1 for the Suzuki reaction, whereas the introduction of electron-withdrawing groups at the edge of the GQD significantly enhanced it. Furthermore, progressively increasing the number of electron-withdrawing groups gradually improved the catalytic performance of NbN@GQD-(NO₂)_<i>n</i> with a low energy barrier of 19.3 kcal mol^-1. Thus, this study presents a rational strategy to design single superatom catalysts by doping noble metal-like superatoms into defective GQDs of different sizes or even a large-sized graphene.