Harnessing Reversible 0D–1D Transformation in Chiral Mn(II) Halides for Smart Circularly Polarized Luminescence Switching and Multi‐Level Encryption

Abstract Circularly polarized luminescence (CPL) active materials with dynamically tunable properties are highly desirable for next‐generation photonics and encryption technologies, yet achieving this through predictable solid‐state structural transformations remains a formidable challenge. Herein, we demonstrate a novel dimensionality‐engineering strategy to realize stimuli‐responsive CPL in chiral hybrid Mn(II) halides. Employing a single chiral cation, R/S‐3‐methylmorpholine, we selectively synthesized two distinct phases: a red‐emissive 1D chain structure with octahedral Mn(II) centers and a green‐emissive 0D structure with tetrahedral coordination. Remarkably, the 0D phase undergoes a rapid and reversible ethanol‐assisted thermal transformation into the 1D phase, accompanied by a striking CPL color switch from green to red. This unique behavior stems from a stimulus‐induced recoordination of Mn–Cl units and reorganization of the hydrogen‐bonding network. Capitalizing on this reversible response and intrinsic chirality, we engineered a sophisticated multilevel photonic encryption platform, encompassing binary dot‐matrix coding, dual‐channel (photoluminescence/CPL) Morse code, and CPL‐based ASCII decryption. This work establishes structural dimensionality control as a powerful paradigm for creating intelligent, CPL‐active materials, opening new avenues for high‐security optical information technologies.