The synthesis of nanoscaled β-Bi₂O₃ starting from the bismuth oxido clusters [Bi₆O₄(OH)₄](NO₃)₆·H₂O, [Bi₂₂O₂₆(OSiMe₂ ^tBu)₁₄], [Bi₃₈O₄₅(NO₃)₂₀(DMSO)₂₈](NO₃)₄·4DMSO and [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉]·2DMSO·7H₂O (OMc = O₂CC₃H₅) under ambient conditions is reported. The metal oxido clusters are regarded as ideal precursors for β-Bi₂O₃ due to their structural relationship with the latter. Nevertheless, different bismuth oxide polymorphs are accessible dependent on the hydrolysis protocol. Hydrolysis over a period of 18 h gave stable α-Bi₂O₃ whereas after 3 min an amorphous material is observed. Annealing of the amorphous material at 370 °C gave nanoscaled β-Bi₂O₃. An unusual high reactivity of the β-Bi₂O₃ particles with SiO₂ and Al₂O₃ is observed at temperatures above 400 °C. Powder X-ray diffraction studies, transmission electron microscopy, diffuse reflectance UV/Vis spectroscopy and nitrogen adsorption measurements are used for characterization of the as-prepared β-Bi₂O₃ nanoparticles. The properties of the β-Bi₂O₃ nanoparticles depend on the starting bismuth oxido clusters with regard to particle size and optical band gap. The β-Bi₂O₃ nanoparticles show excellent photocatalytic activity as demonstrated by dye decomposition (rhodamine B, methyl orange, methylene blue and orange G) under visible light.

Photocatalytic studies under visible light irradiation using nanosized β‐Bi₂O₃ are reported. β‐Bi₂O₃ nanoparticles are prepared starting from the well‐defined bismuth oxido cluster [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉]⋅2 DMSO⋅7 H₂O (OMc=O₂CC₃H₅) using a straightforward hydrolysis and annealing protocol. Powder X‐ray diffraction studies, transmission electron microscopy, diffuse reflectance UV/Vis spectroscopy and nitrogen adsorption measurements (using the Brunauer–Emmett–Teller (BET) theory) are used for the characterization of the as‐prepared β‐Bi₂O₃. By time‐dependent annealing, the crystallite size can be controlled between (17±2) nm and (45±5) nm with BET surface areas of 7 to 29 m² g⁻¹. The indirect band gap of the as‐prepared β‐Bi₂O₃ amounts to (2.15±0.05) eV. The decomposition rates for rhodamine B (RhB) solutions are in the range of 2.46×10⁻⁵ to 4.01×10⁻⁴ s⁻¹ and depend on the crystallite size, amount of catalyst and concentration of RhB. Photocorrosion experiments have shown the formation of Bi₂O₂CO₃ after several catalytic cycles. However, the catalyst can be recycled to phase‐pure β‐Bi₂O₃ nanoparticles by annealing for one hour under argon atmosphere at 380 °C. Furthermore, the photocatalytic activity of as‐prepared β‐Bi₂O₃ nanoparticles for the decomposition of phenol, 4‐chlorophenol, 2,4‐dichlorphenol, 4‐nitrophenol, triclosan and ethinyl estradiol is demonstrated.

The reaction of the basic bismuth nitrate [Bi₆O₄(OH)₄](NO₃)₆·H₂O with sodium methacrylate in DMSO gave [Bi₃₈O₄₅(OMc)₂₄(DMSO)₉]·2DMSO·7H₂O (OMc = O₂CC₃H₅), which is highly soluble in organic solvents. By copolymerization of the bismuth oxido cluster with methyl methacrylate transparent, radiopaque organic–inorganic hybrid materials were obtained.