Photophysical characterization of methyl viologen ion-exchanged within a zirconium phosphate framework

The photophysical properties of 1,1′-dimethyl-4,4′dipyridinium (methyl viologen, MV²⁺) intercalated within zirconium phosphate (ZrP) were investigated. The intercalation of MV²⁺ within ZrP was achieved by ion-exchange using a hydrated form of ZrP with six water molecules per formula unit and an interlayer distance of 10.3 Å. The intercalation yields a new phase with an interlayer distance up to 10.6 Å. The MV²⁺-exchanged ZrP material was characterized using elemental analysis, XRPD and IR data. The MV²⁺-exchanged ZrP materials show a red shift in the UV-Vis spectra in contrast with solution. The photoexcitation of nitrogen purged, MV²⁺-exchanged ZrP water suspensions with UV light leads to fluorescence emission with a maximum at 337 nm. The photoexcitation of MV²⁺-exchanged ZrP suspensions without nitrogen purging yields two fluorescence emissions with maxima at 337 and 450 nm. The emission in the visible region can be attributed to a photodecomposition product. The fluorescence quantum yields indicate that the emission of MV²⁺-exchanged ZrP is of the same order of magnitude as that of MV²⁺ in water indicating a strong deactivation of the excited state by non-radiative pathways.