Dynamic Tunable Multifunctional Platform BiOCl: Yb ³⁺ /Ho ³⁺ With Multimodal Photo‐Response for Intelligent Anti‐Counterfeiting

ABSTRACT Controlling excitation‐response and emission tunability in luminescent materials is crucial for high‐security anti‐counterfeiting, but current multimodal materials primarily suffer from static single‐color emission under fixed stimuli, limiting their security potential. Developing a single material with dynamic multichannel emission remains a major challenge. Herein, a multifunctional BiOCl: Yb 3+ , Ho 3+ material with multi‐excitation luminescence, rapid photochromism, and light‐driven dye discoloration has been explored. It emits green up‐conversion emission from Ho 3+ under 980 nm excitation; and broad‐band blue emission from the embedded carbon dots produced during the materials synthesis centers at 470 nm under the excitation of 365 nm, accompanied by a rapid photochromic transition from pale‐yellow to black and reversible process by thermal treatment. The oxygen vacancies in BiOCl: Yb 3+ , Ho 3+ have been confirmed to responsible for the reversibility of the rapid photochromic effect of samples, which also enhance the efficient photocatalytic degradation of Rhodamine B and enable the controllable dye discoloration. These features are integrated into BiOCl: Yb 3+ , Ho 3+ to establish a dynamically tunable multimodal platform, offering a new “concealment‐activation‐erasure‐rewriting” paradigm for next‐generation high‐security anti‐counterfeiting and optical information encryption.