Charge-polarized metal site pairs trigger new opportunities in photocatalysis

Photocatalysis technology shows great potential to address global energy and environmental issues. However, several bottlenecks existed in different photocatalytic reactions, such as N₂ molecules activation, C–C coupling for C₂₊ products generation. Benefiting from the unique coordination and electronic states, the emerging charge-polarized metal site pairs with appropriate design show enormous potential to address these issues. This critical review summarizes the recent progress of charge-polarized metal site pairs for photocatalysis. The multifarious types of charge-polarized metal site pairs are introduced with an emphasis on formation principle, such as charge-polarized metal₁-metal₁ pairs, charge-polarized metal₁-metal₂ pairs, metal₁-metal₂ single atom pairs. The crucial roles of various charge-polarized metal site pairs in photocatalysis are highlighted, including optimizing charge separation, boosting molecular activation, tuning reaction paths, triggering C–C coupling, and boosting C–N coupling. Additionally, the energy-related photocatalytic applications based on the charge-polarized metal site pairs are discussed, with the elucidation of relationship between the accurate local atomic configuration and photocatalytic performance. Finally, we end this review with a look into the opportunities and challenges of charge-polarized metal site pairs for photocatalysis in future study.