Achieving Room-Temperature Phosphorescence through Ligand-to-Ligand Energy Transfer in Dual-Ligand Metal–Organic Frameworks

Phosphorescent metal-organic frameworks (PMOFs) have attracted much attention due to their ultralong emission lifetime and structural tunability. The preoccupant strategies of constructing PMOFs mainly refer to the simple physical confinement of organic phosphors in porous MOFs, but the phosphors may easily escape from the pores and further affect the stable performances consequently. Here, three dual-ligand MOFs of Cd-TD1, Cd-TD2, and Cd-TD3 are synthesized by in situ dual-ligand coordination to achieve efficient room-temperature phosphorescence (RTP), and the RTP behaviors are greatly boosted by ligand-to-ligand energy transfer. All three dual-ligand MOFs exhibit bright and long afterglows, with the longest phosphorescence lifetime reaching 210 ms. By adjusting the guest conjugation to regulate the energy level, tunable RTP color in dual-ligand PMOFs can be further controlled via ligand engineering. The stable PMOFs also demonstrate great potential in advanced anticounterfeiting encryption by leveraging the time-dependent color change.