Coordination-Environment-Mediated Selective Recognition of As(III) and Cu(II): Ion-Specific Charge Transfer at Pt Single-Atom Sites on α-Fe2O3 Nanospindles.

Single-atom catalysts (SACs) with a single active-site type struggle to independently regulate multiple reactants or intermediates, causing competitive adsorption and coupled charge-transfer pathways. Here, vacancy-directed Pt single atoms are engineered on α-Fe2O3 to enable ion-specific interfacial pathways. By controlling Pt loading, isolated Pt atoms are selectively stabilized at Fe vacancies and O vacancies, forming two sites with distinct coordination structures and electronic properties. Structural characterization and DFT calculations reveal PtFe at electron-deficient Fe vacancies is more conducive to Cu(II) adsorption and electron transfer, while PtO at electron-rich O vacancies is more conducive to As(III) adsorption and reduction, thus achieving ion-selective adsorption and charge transfer on the same surface. This site-specific division of labor separates the pathways of coexisting As(III) and Cu(II), suppresses signal cross-interference, and enables highly selective electrochemical recognition. Tailoring local coordination environments therefore offers a broadly applicable strategy for constructing functionally differentiated interfaces with selective recognition capability.