Supramolecular Fixation of Three Amines using Cobalt Tetraphenyl-porphyrin for SO₂ Removal

In this work, supramolecular fixation of three amines, including aniline, ethylenediamine, and diethylamine, using cobalt tetraphenylporphyrin (CoTPP) for SO₂ removal was studied using UV-Vis and fluorescence measurements. The UV-Vis spectra showed that increasing amines concentrations resulted in bathochromic shift for CoTPP Soret absorption band (B band). Once SO₂ was introduced, it competed with CoTPP for aniline, ethylenediamine, and diethylamine, which eventually led to the release of CoTPP and the change of solution colour/absorption band. After that, the CoTPP was regenerated and got back to the first state. The fluorescence spectra offered that CoTPP interacted with aniline, ethylenediamine, and diethylamine to form 1:1 molecular adducts. The interactions of CoTPP with aniline, ethylenediamine, and diethylamine were entropy-driven. The interaction of CoTPP with aniline and diethylamine was endothermic, and that with ethylenediamine was exothermic. Ethylenediamine presented a stronger binding constant value for CoTPP, so it was considered as a potential agent for SO₂ removal.