Mixed-ligand-based luminescent MOFs as chemical sensors for toxic environmental contaminants

Luminescent metal-organic frameworks (LMOFs) are gaining significant attention for their enhanced fluorescent properties and potential in sensing applications. The mixed-ligand approach, which combines different N, N'donor and polycarboxylate ligands, has been widely employed for the synthesis of MOFs, significantly enhancing their fluorescent properties. This review focuses on the use of mixed-ligand MOFs for fluorescent sensing, particularly targeting heavy metals, nitro-aromatics, and organic molecules. The first section discusses the mechanisms of fluorescence sensing that guide the design and preparation of MOFs tailored for specific analytes. The second section compiles literature on the use of transition and lanthanide metal-based luminescent mixedligand MOFs as fluorescent sensors for detecting heavy metal ions (e.g., Fe3+, Al3+, Cr3+, Hg2+, Pd2+, Cu2+), anions (e.g., CrO42-, Cr2O72-), nitro-aromatics (e.g., nitrobenzene, nitrophenol, trinitrophenol (TNP)), and organic molecules (e.g., uric acid, ascorbic acid, picric acid). By consolidating this information, the review highlights the progress and potential of mixed-ligand MOFs in fluorescent sensing, paving the way for future research and development.