Multisite Fine‐Tuning in Hybrid Cadmium Halides Enables Wide Range Emissions for Anti‐Counterfeiting

Abstract Achieving tunable emissions spanning the spectrum, from blue to near‐infrared (NIR) light, within a single component is a formidable challenge with significant implication, particularly in tailoring multicolor luminescence for anti‐counterfeiting purposes. In this study, we demonstrate a broad spectrum of emissions, covering blue to red and extending into NIR light in BPy 2 Cd X 4 : x Sb 3+ (BPy=Butylpyridinium; X =Cl, Br; x =0 to 0.08) through precise multisite structural fine‐tuning. Notably, the multicolor emissions from BPy 2 CdBr 4 : Sb 3+ manifest a distinctive pattern, transitioning from blue to yellow in tandem with the host BPy 2 CdBr 4 and further extending from yellow to NIR with its homologous BPy 2 CdCl 4 : Sb 3+ , resulting in the simultaneous presence of intersecting and independent emission colors. Detailed modulation of chemical composition enables partial luminescence switching, facilitating the creation of diverse patterns with multicolor luminescence by employing BPy 2 Cd X 4 : x Sb 3+ as phosphors. This study for the first time successfully implements several groups of tunable emission colors in a single matrix via multisite fine‐tuning. Such an effective strategy not only develops the specific relationships between tunable emissions and adjustable compositions, but also introduces a cost‐effective and straightforward approach to achieving unique, high‐level, plentiful‐color and multiple‐information‐storage labels for advanced anti‐counterfeiting applications.