A two-dimensional indium-based MOF as a stable and highly sensitive fluorescent sensor for nitrofural

A two-dimensional indium-based metal-organic framework [InL₃(H₂O)]_n (L = 5'-(4-carboxyphenyl)-[1,1':3',1″:4″,1‴-tetrabiphenyl]-4,4‴-dicarboxylic acid) (referred to as SLX-10) has been synthesized by a solvothermal method; it exhibits excellent photoluminescence properties and demonstrates precise recognition and detection capabilities toward nitrofural (NF), with a detection limit as low as 1.3 μM and a quenching constant (K_sv) as high as 4.8 × 10⁴ M^-1, better than some reported MOFs for the fluorescence detection of NF. Even in the presence of artificially introduced interfering substances, the fluorescence of SLX-10 can still be accurately quenched by NF, and the material maintains an excellent fluorescence response performance for at least five detection cycles. Through density functional theory calculations, it was found that electrons can easily transfer from SLX-10 to NF. Upon also considering ultraviolet-visible absorption spectra, the fluorescence quenching mechanism is believed to involve the synergistic effect of photoinduced electron transfer and fluorescence resonance energy transfer.