Engineering Solvent‐Coordinated Heterometallic–Organic Frameworks for Wide‐Range Tuning of Ultralong Room Temperature Phosphorescence toward Time‐Resolved Anticounterfeiting

Metal-organic frameworks (MOFs) have been proven promising ultralong room temperature phosphorescence (RTP) materials for anti-counterfeit due to their unique optical properties. However, it remains a major challenge to achieve the desired phosphorescent properties due to the limited regulatory methods and indistinct mechanism. Herein, the coordination solvent and second metal ion co-strategy is firstly proposed to prepare seven robust heterometallic-organic frameworks (HMOFs) with two configurations: ZnMg/Ca-sol [sol = H2O, dimethylformamide (DMF), dimethylacetamide (DMA), and formyldiethylamine (DEF)] and ZnSr/Ba-H2O, exhibiting the different ultralong RTP. The tunable phosphorescence lifetimes within 14.5-195.4 ms are achieved gradually by altering the type of alkaline earth metals, coordination solvent, and hydrogen-bonding in the HMOFs. Significantly, the theoretical calculations reveal that the promotion of spin-orbit coupling by heavy metals and the rigid constraint on the skeleton by solvent result in excellent balance between high phosphorescence quantum yield (ФP) and long lifetime, especially for ZnSr-H2O (6.8%, 195.4 ms). Depending on the wide-range tuning of ultralong RTP and great stability, the HMOFs are successfully applied in spatial-time resolved anti-counterfeiting and multi-level information encryption. This work may provide a new approach to designing target phosphorescent materials while resolving the contradiction between high ФP and long lifetime.