Highly selective and efficient adsorption dyes self-assembled by 3D hierarchical architecture of molybdenum oxide

A novel hierarchical architecture of molybdenum trioxide (α-MoO3) was synthesized via a facile template-free hydrothermal route directly by using molybdenyl acetylacetonate and acetic acid as the starting materials. SEM and TEM observations indicate that this microstructure is a flower-like microsphere with a diameter of 15 to 20 μm. It consists of numerous nanobelts with (001) preferential crystallographic plane which seemingly grow from the sphere-like core and the nanobelts were 100 nm in width, 4 μm in length and 15–20 nm in thickness. The molybdenum oxide-based hierarchical microstructure exhibits a fast and selective adsorption to the adsorbate organic pollutants with benzoic acidic group for the first time. The removal rate of α-MoO3 to RhB reaches 97.9% in 10 min at a RhB concentration of 20 mg L−1 at room temperature, which is significantly fast as well as the commercial active carbon and the maximum adsorption capacity is 9 times that of the commercial activated carbon at a RhB concentration of 200 mg L−1. The mechanism for selective adsorption was discussed according to the results of IR, XPS and theoretical calculation. XPS and IR spectra confirm the RhB molecules adsorbed on the surface of MoO3 and interacted with Mo ions. DFT calculations indicate that the larger delocalization of the organic groups, the larger amount of charges transfer, the higher binding energy of organic molecules to the (001) lattice plane of α-MoO3 surface.