Photochromic Metal‐Organic Frameworks With White‐Light Emission, and Multicolor Afterglow for Advanced Anti‐Counterfeiting and Encryption

Rational design of metal-organic frameworks (MOFs) with integrated long-afterglow luminescence (LAL), photochromism, and multicolor emission remains desirable yet challenging for advanced anti-counterfeiting and information encryption applications. Herein, a series of halide-tuned X-MOFs (X = Cl, Br, and I) integrating photoluminescence and photochromism were synthesized via hydrothermal reaction of an electron-deficient triazine-based ligand (L) with CdX₂. The rigid framework, combined with halogen engineering, enables tunable multi-path luminescence in these X-MOFs. Meanwhile, the involvement of halogens and charge distribution of the ligand facilitate effective photoinduced electron transfer. Upon prolonged UV exposure, photochromic and photothermal responses result directly from the accumulation of HL· free radicals. Owing to the coexistence of photoinduced electron-transfer quenching and charge-transfer emission, the X-MOFs exhibit not only irradiation-time-, excitation-, and temperature-dependent cold-to-warm white-light tunability, but also excitation-, temperature-, and time-responsive multicolor LAL spanning green to yellow or orange. Combined theoretical analyses elucidate the multipath luminescence originating from intra- and intermolecular charge transfer in the rigid framework, and photochromic behavior arising from electron transfer between the pyridine and triazine in the ligand backbone. These multifunctional MOFs exhibit great promise for high-security information encryption and anti-counterfeiting, offering a straightforward strategy for designing advanced luminescent materials.