Confined Assembly of Well-Defined Single-Unit Chain with Charge Delocalization for Boosting Catalysis.

The ultimate miniaturization of catalysts to single-atomic dimensions offers a promising route to maximize the catalytic performance through fully exposed active sites and precisely tailored electronic structures. However, the synthesis of atomically precise one-dimensional single-cluster or single-atom catalysts with the simplest periodicity remains challenging due to their thermodynamic instability. Here, we report a general strategy for fabricating single-unit-chain catalysts confined within single-walled carbon nanotubes (SWCNTs), where charge delocalization dramatically enhances the catalytic performance. Through a liquid-phase assembly approach, diverse clusters and atoms can be uniformly packed into ordered single-unit chains inside SWCNTs, irrespective of their electronic properties or solubility. These identical, well-defined single-unit chains maintain intimate contact with the conductive graphene walls of SWCNTs, enabling tunable positive or negative charge delocalization across the nanotube surfaces. The resulting catalysts demonstrate remarkable activity enhancements in both redox and coupling reactions, exhibiting rate constants 7.5∼28 times greater than their isolated cluster counterparts. Mechanistic studies reveal that charge delocalization simultaneously increases the density of active sites and reduces the activation barriers. This synthetic approach and catalytic mechanism show universal applicability to various single-chain catalysts. These systems maintain nearly undiminished activity in 230 h continuous-flow reactions, highlighting their exceptional stability for practical applications.