Wheel–Sandwich Polyoxomolybdate Chains Assembled from Integrated {Mo6} Wheels and {Mo6–Mn–Mo6} Motifs

The integration of distinct polyoxometalate (POM) building units offers opportunities to tailor their structural and electronic properties. Herein, we report two new polyoxomolybdates, MnPMo and NaMnPMo, featuring one-dimensional wheel–sandwich architectures composed of hexanuclear {Mo6} wheels and {Mo6–Mn–Mo6} units linked by phosphate groups. Single-crystal X-ray diffraction reveals different degrees of framework condensation: MnPMo contains 124 framework oxygen atoms per Mn4 unit, whereas NaMnPMo contains 120, with Na+ incorporated for charge compensation. Density functional theory calculations show that mixed-valence Mo(V)/Mo(VI) centers in MnPMo contribute to a high density of states near the Fermi level, while NaMnPMo exhibits greater electronic delocalization. These findings establish a relationship between framework condensation and electronic structure. Furthermore, NaMnPMo/TiO2 exhibits enhanced photocatalytic activity toward ciprofloxacin under simulated solar irradiation, achieving nearly complete removal within 60 min. Electron paramagnetic resonance results indicate enhanced reactive oxygen species generation, consistent with improved charge separation. This work presents a new wheel–sandwich POM architecture and highlights framework condensation as a structural parameter relevant to electronic properties.