Self-assembly of MnO2 nanostructures into high purity three-dimensional framework for high efficiency formaldehyde mineralization

Self-assembly has been considered as a powerful strategy for constructing the inorganic nanoparticles into macroscopic three-dimensional frameworks. Herein, a high-purity three-dimensional manganese dioxide (3D-MnO2) framework was successfully self-assembled via ice-templating approach starting from MnO2 nanoparticles without assistance of functionalization or stabilization organics. The enhanced van der Waals force between the MnO2 building blocks by the squeezing of ice crystals is the main assembly force for the construction of 3D-MnO2 framework. The resulting 3D-MnO2 framework exhibits significantly increased in catalytic activity, which could continuously and efficiently transform HCHO into CO2 at room temperature. The excellent activity of 3D-MnO2 framework could be attributed to its strong water adsorption and activation ability, which can not only regenerate the consumed hydroxyl groups, but also enhance the desorption of carbonate species and reduce the accumulation of intermediate species. The self-assembly strategy presented herein may be suggestive for the purification of organic pollutants in indoor air.