Supramolecular recognition of functional magnesium tetraphenylporphyrin (MgTPP) with pyrrolidine for SO2 capture was investigated in CH2Cl2 by steady-state fluorescence and UV-vis absorption spectroscopic techniques. The UV-vis spectra showed that the interaction of MgTPP with pyrrolidine resulted in red shift of 2 nm for MgTPP Soret absorption band. Once introduced, SO2 competes with MgTPP for pyrrolidine, which eventually leads to the release of MgTPP. The fluorescence spectra suggested that MgTPP interacted with pyrrolidine to form 1 : 1 molecular adducts, and showed that the binding of MgTPP with pyrrolidine with the association constants (Kassoc) of (0.86 to 1.19) is not only exothermic but enthalpy-driven with ΔH=-15.805 kJ mol^(-1), ΔS=-52.727 J mol^(-1) K1, and ΔG=-214.444 J mol^(-1) at T=296.15 K.