The unclear origin of the photoluminescence (PL) in single-phase white-light materials based on silver nanoclusters (Ag–NCs) confined within zeolite hosts has hindered the rational design of composites with tunable emission properties. In this study, we combined X-ray Excited Optical Luminescence (XEOL)–X-ray Absorption Fine Structure (XAFS) at the silver K-edge and X-ray Absorption Near Edge Structure (XANES) at the sulfur K-edge to unravel the structure of the species responsible for the white emission in Ag/S-SOD zeolites. Our findings reveal that the white luminescence observed in these materials arises from the formation and stabilization within the sodalite cages of a mixture of Ag3O, Ag4O2, and Ag6O4 NCs coordinated by oxygen ligands, each having specific emission features. The precise tone of the white-light emission can be further tuned by adjusting their relative fractions. The remarkable emission stability of these materials originates from the closed structure of the SOD zeolites and the formation of a network of Ag–NCs and co-cations stabilized by oxygen ligands, whose coordination environment is modulated by transient silver–sulfur interactions occurring during synthesis. Ultimately, Ag/S-SOD zeolites are not only efficient single-phase and emission-tunable phosphors but also robust platforms for studying the structure–property relationships of confined metal NCs.
