Abstract: Metal-organic frameworks (MOFs) are widely used in the identification and detection of pollutants, showing great potential particularly in the fluorescent detection of heavy metal ions and nitro compounds. However, their stability and fluorescence performance are often limited by the nature of the coordination bonds. In this study, novel thiophene-bridged ligands with planar conjugated extension and controllable chain length were synthesized via Stille coupling and NBS selective bromination strategies. These ligands were successfully used to construct highly stable and fluorescence-enhanced thiophene-based MOFs (TPD-1 and TPP-1). The application of these materials in the fluorescent recognition of metal ions and nitro compounds was systematically investigated. The results indicate that both crystals are formed by connecting hexanuclear eight-connected secondary building units (Zr6(μ3-O)8(COO)8(H2O)8) with organic ligands. TPD-1 belongs to the tetragonal crystal system with the I41/amd space group, while TPP-1 belongs to the cubic crystal system with the Fmmm space group. Among them, the extended conjugated aromatic framework of TPP-1 effectively enhances its stability in aqueous solutions and under acidic or basic conditions, while promoting interactions with target analytes. This enables TPP-1 to exhibit excellent fluorescence sensing performance for both Fe3+ and aromatic nitro compounds, with a quenching efficiency exceeding 93% and a Ksv constant reaching the order of 104 M-1.

Key words: Thiophene-bridged ligand; metal-organic frameworks, fluorescence recognition, Fe³⁺, aromatic nitro compounds