Structural and theoretical investigations of 3D Ni-formate framework: Exploration as selective fluoroprobe for detection of industrial solvents

Abstract

This research reported the solvothermal synthesis of a nickel-based metal formate framework (MFF) templated by protonated amines which served as a sensing platform, for the detection of industrial solvents, namely acetone and ethyl methyl ketone, with exceptional specificity and recyclability for up to seven cycles. The synthesised Ni-formate framework was characterised using single crystal X-ray diffraction (SCXRD), Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDS), and thermogravimetric analysis (TGA). The DFT analyses offer a comprehensive estimation of charge density distribution and the electron localisation function (ELF) of the Ni-formate framework. The exceptional emissive properties of the Ni-formate framework, examined in various chemical solvents, were employed to create MFF-based ’turn-off’ luminescence sensing for organic molecules containing aldehyde and ketone functional groups. The findings demonstrated that our proposed probe provide exceptional recognition capability for acetone and ethyl methyl ketone among the various carbonyl compounds probed. The Ni-formate framework with both commercial solvents demonstrates a strong linear correlation between the relative fluorescence intensity (Io/I) and solvent concentration within the range of 0–100 μM. The detection limits for spectrofluorometric analysis of acetone and EMK were determined to be 3.3 µM and 3.522 µM, respectively. The Stern–Volmer constant was calculated as 1.01 × 10⁶ M⁻¹ for acetone and 1.02 × 10⁶ M⁻¹ for EMK, indicating substantial interaction among Ni-MFF and the solvents. The Ni-formate framework exhibited fluorescence quenching approximately with in one minute of exposure to an aqueous solution containing acetone and EMK. The study demonstrates the potential of nickel-based metal formate framework sensor for rapidly identifying industrial solvents with significant sensitivity, good selectivity, and recyclability without a decline in fluorescence efficiency.