Fe2+/Fe3+ based MOIFs + dye interaction study: Thermodynamic and kinetic analysis estimated through spectrophotometrically

Abstract

Herein, the interaction study of organic dyes with newly reported metal organic ionic frameworks (MOIF) based on [Fe(CN)6]3-/[Fe(CN)6]4-/[Fe(CN)5NO]2- and cetylpyridinium cation, investigated through spectrophotometric method. Measurements were carried out at 303.15, 308.15 and 313.15 K where interaction found to be decreased with increase in temperatures. The 60–90% maximum interaction was noted for [Fe(CN)5NO]2- based MOIF with all chosen dyes at 303.15 K inferring the high interaction ability associated with dissymmetry of this MOIF due to presence of different ligands. The oxidation state and hydrophilicophobic domains of MOIFs have been found accountable for the stronger interaction where Fe2+ with high hydrophobicity was found more interacting as compared to Fe3+ with less hydrophobicity. The activation parameters ΔG0, ΔH0 have been found greater for MOIFs and methylene blue dye systems due to stronger interaction of their hydrophobic domains. The ΔS0 noted greater for [Fe(CN)5NO]2- based MOIF showing the impact of availability of interacting sites and distortion in symmetry. The isotherm analysis has inferred about the maximum uniform distribution of binding energy, favorability of interaction, interaction capacity and intensity, was associated with methylene blue and MOIFs systems. The positive slope (2.303/K) of a plot of log(Ao/At) vs t (time) inferred the first order kinetic of MOIF and chosen dyes.