Exploring Fe3+ cation exchange dynamics in fluorescent MIL-53(Al) MOF: Solid-state photoluminescence and structural insights

Flexible luminescent MOFs have gained significant interest since they combine the advantages of ratiometric fluorescence with the ability to modify the structure to accommodate a large variety of guest molecules. This study has investigated the influence of different concentrations of Fe 3+ cations on the MIL-53(Al) MOF by employing a comprehensive array of characterization techniques on the solid-state samples, aiming to relate the optical response with the structural modifications. Structural and thermalgravimetric findings evidenced modifications in peak positions, intensities, and an improved thermal stability of Fe 3+ -exchanged MIL-53(Al) samples compared to the pristine MOF, thus indicating structural changes induced by the incorporation of Fe 3+ cations. Moreover, as the Fe 3+ concentration increases, a quenching of the UV and blue photoluminescence bands is observed. Hence, shedding light on the complex interplay between Fe 3+ cation exchange, the photoluminescence and structural properties of solid-state MIL-53(Al) MOF, can provide valuable insights for the rational design and engineering of MOF-based materials for various applications, including sensing, catalysis, and optoelectronics. • Investigation of Fe³⁺ cation exchange in MIL-53(Al) MOF using diverse structural and optical techniques. • Effects of different activation temperatures on solid-state photoluminescence (PL). • Enhanced thermal stability upon Fe³⁺ incorporation. • UV and visible photoluminescence (PL) quenching correlated with Fe³⁺ concentration. • Interplay between cation exchange, structural modifications, and luminescence.