Rational design and synthesis of SnO 2 -encapsulated α -Fe 2 O 3 nanocubes as a robust and stable photo-Fenton catalyst

Abstract In situ transformation of metal-organic frameworks (MOFs) is becoming a fascinating strategy to construct porous metal oxides with excellent performance in many fields. In this work, Prussian blue (PB) nanocubes are employed as the precursor of porous Fe2O3 to fabricate SnO2-encapsulated α-Fe2O3 (Fe2O3@SnO2) nanocubes by pre-coating Sn(OH)Cl on the surface of PB nanocubes. It is very interesting to find that SnO2 shells can not only preserve the microstructure of Fe2O3 nanocubes from high-temperature treatment, but also facilitate the phase variation from metastable γ/β-phase to stable α-phase. The thickness of SnO2 shells can be controlled by manipulating the amount of stannous chloride. When Fe2O3@SnO2 nanocubes are applied as heterogeneous photo-Fenton catalysts, they will exhibit much better catalytic efficiency for the degradation of Rhodamine B (RhB) than PB-derived Fe2O3 and commercial α-Fe2O3. The characterization results reveal that Fe2O3@SnO2 nanocubes have similar catalytic mechanism to conventional α-Fe2O3, and stable microstructure and preferable crystalline phase are primarily responsible for this significant enhancement. Some influential factors, including H2O2 concentration, catalyst dosage, pH value, and reaction temperature are investigated and analyzed in details. Moreover, Fe2O3@SnO2 nanocubes can maintain their catalytic efficiency during the repeated batch experiments. We believe Fe2O3@SnO2 nanocubes can be a new kind of high-performance green heterogeneous catalyst for the degradation of organic pollutants, and this study may provide a new idea to upgrade the performance of some conventional catalysts by rational design in the future.