Synthesis of Tb and Dy MOFs Using Pyridazine-3,6-Dicarboxylic Acid: Dual-Function of Tb-MOF for Luminescent Sensing of o-NBA and Riboflavin and Photocatalytic Degradation of Rhodamine B

This study explores the synthesis, characterization, and multifunctional applications of two lanthanide-based metal-organic frameworks (MOFs), [Ln₂(Pym-3,6-dca)(O₂^-)(H₂O)] (Ln = Tb, Dy), using pyridazine-3,6-dicarboxylic acid as a rigid N, O-donor linker. Both MOFs crystallize in the I4₁/a space group and exhibit high thermal stability. Tb-MOF shows intense green photoluminescence with a long excited-state lifetime (τ = 3.967 ms), enabling highly sensitive ″turn-off″ fluorescence sensing of o-nitrobenzoic acid (LOD = 0.30 ppm) and riboflavin (LOD = 0.31 ppm) in aqueous solutions. The luminescence quenching mechanism involves resonance energy transfer and photocompetitive absorption, supported by spectral overlap analysis and DFT-calculated energy levels. Tb-MOF also acts as an efficient photocatalyst for the visible-light-induced degradation of Rhodamine B, achieving 96.45% degradation in 80 min. The activity is enhanced by H₂O₂, forming hydroxyl radicals. Radical trapping experiments confirm a multipathway degradation mechanism. Tb-MOF outperforms Dy-MOF in both sensing and catalytic applications, highlighting its potential for environmental monitoring and biomedical sensing. This study underscores the use of pyridazine-based linkers in developing multifunctional lanthanide MOFs with tunable optical and catalytic properties.