Engineering Solvent-Coordinated Heterometallic-Organic Frameworks for Wide-Range Tuning of Ultralong Room Temperature...

Metal-organic frameworks (MOFs) have been proven promising ultralong room temperature phosphorescence (RTP) materials for anticounterfeit 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 costrategy 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 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 (Ф_P) 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 anticounterfeiting and multilevel information encryption. This work may provide a new approach to designing target phosphorescent materials while resolving the contradiction between high Ф_P and long lifetime.