Green synthesis of cavity-containing manganese oxides with superior catalytic performance in toluene oxidation

•Green synthesis of cavity-containing manganese oxides by hydrothermal method.•High catalytic performance in toluene oxidation with total conversion at <200 °C.•Highly reactive oxygen surface species at the tetragonal distorted cationic sites.•Presence of structural water and internal cavities in the Mn3O4 crystalline structure.