The invention discloses a preparation method of foam-shaped mesoporous amorphous B-N-O-H nano-materials. According to the preparation method, 1- butyl-3-methylimidazolium hexafluorophosphate is used as an ionic liquid, the foam-shaped mesoporous amorphous B-N-O-H nano-materials are successfully synthesized in a liquid phase plasma device, and the foam-shaped mesoporous amorphous B-N-O-H nano-materials are used as electrodes to be applied to electronic adsorption of methylene blue (MB). With the specific foam-shaped mesoporous structure and relatively high specific surface area, the nano-materials have ultra-high electronic adsorption capacity and excellent selectivity adsorption performance. The material, in the field of sewage purification, has a wide application prospect on enrichment or even complete separation of dyes in a sewage treatment process. In addition, the materials also can be used for enrichment of light metal salts and heavy metal ions.