Tailoring structural and luminescent properties of solid-state MIL-53(Al) MOF via Fe3+ cation exchange

Metal-Organic Frameworks (MOFs) have emerged as promising candidates for detecting metal ions owing to their large surface area, customizable porosity, and diverse functionalities. In recent years, there has been a surge in research focused on MOFs with luminescent properties. These frameworks are constructed through coordinated bonding between metal ions and multi-dentate ligands, resulting in inherent fluorescent structures. Their luminescent behavior is influenced by factors like structural composition, surface morphology, pore volume, and interactions with target analytes, particularly metal ions. This study investigates the impact of Fe3+ cation exchange on the structural, thermal, and photoluminescent (PL) properties of MIL-53(Al) MOF samples. Incorporating Fe3+ ions induces structural distortions, altering coordination environments and leading to amorphization. Enhanced metal-ligand bonds boost thermal stability, delaying decomposition processes. Raman peak changes reflect ionic and charge disparities, disorder from cation exchange, and electronic effects. PL emission spectra variations reveal MOF framework influence on emission characteristics, with Fe3+ exchange quenching PL intensity and shortening lifetimes due to structural distortions and stronger linker binding, favoring non-radiative decay. These findings underscore the complexity of MOF interactions, crucial for applications like catalysis, gas storage, and luminescent devices. Cation exchange emerges as a promising strategy for tailoring MOF properties to specific needs.