Information Encryption via Spirooxazine-Based Photochromic Chiral Metal-Organic Frameworks

Spirooxazine (SO) derivatives, an important class of stimulus-responsive chromic materials, are often not photochromically active in the solid state. Metal-organic frameworks (MOFs) provide a promising platform to overcome this limitation. Here, we report the design and synthesis of photochromic chiral MOFs (R/S-MOFs-TPSO). The pillared-layer framework consists of paddle-wheel dinuclear Zn₂(COO)₄ secondary building units (SBU) bound to chiral camphoric acid and spirooxazine derivative linkers. This architectural design effectively imparts solid-state photochromism to the spirooxazine moieties. The resulting R/S-MOFs-TPSO exhibits a rapid photoresponse, high color contrast, and fully reversible photochromism, with synergistic changes in both color and fluorescence intensity upon ultraviolet (UV) irradiation. The materials demonstrate swift, reversible color transitions from white to blue to purple, along with highly efficient fluorescence quenching (up to 98.3%). Concurrently, the photochromic behavior induces alterations in the circular dichroism (CD) spectrum, including signal amplification and the appearance of new peaks. This synergistic control over color and fluorescence suggests promising applications in advanced anticounterfeiting and information encryption technologies based on dual optical authentication.