Achieving Fluorescent Colour Tunability in High‐Luminescence MOF‐76 via Hydrothermal Annealing and Lanthanide Ions Co‐Doping

ABSTRACT To date, most luminescence studies on MOF‐76 have focused on tetragonal Tb 3+ ‐doped and Tb 3+ /Eu 3+ co‐doped systems. In this work, MOF‐76(Gd, Dy) and MOF‐76(Gd, Tb, Dy, Eu) were synthesised for the first time and subsequently subjected to hydrothermal annealing in the presence of polyvinylpyrrolidone (PVP) as a dispersant. Annealing induced a tetragonal → monoclinic phase transition in MOF‐76 and transformed the morphology from rods into highly crystalline, transparent nanosheets. As a result, the emission intensity of annealed MOF‐76(Gd 0.98 , Dy 0.02 ) increased by approximately 25‐fold and its photoluminescence quantum yield (PLQY) improved from 2.33% to 18.60%. These enhancements enabled the combination of hydrothermal annealing with a lanthanide co‐doping strategy to achieve precisely tunable, highly luminescent colours in the multi‐doped MOF‐76(Gd, Tb, Dy, Eu) system. In the annealed materials ( a MOFs), efficient Tb 3+ → Dy 3+ and Dy 3+ → Eu 3+ energy transfer pathways were identified. Owing to their high luminescence and colour tunability, the resulting materials demonstrated practical applicability in colour‐tunable fluorescent anti‐counterfeiting and, when combined with N‐CDs@starch, in white‐light‐emitting LED devices.