Display omitted •SA/DE@ZIF-8 microspheres with uniform size were prepared by electrostatic spray technology.•SA/DE@ZIF-8 microspheres have porous and ultra-high specific surface area.•Maximum adsorption capacity of Cu(II) was 599.07 mg/g.•Composite microspheres provide a carrier for ZIF-8, easy to recycle and reuse. Diatomite (DE)-based sodium alginate (SA) loaded ZIF-8 composite microspheres were prepared by high-voltage electrostatic spray technology. SA/DE microspheres were prepared by SA and acid-base-regulated silica sol solution. Ultra-small ZIF-8 was grown on SA/DE microspheres by in-situ synthesis method to obtain ultra-high specific surface area composite microspheres. The morphology and particle size of the composite microspheres were analyzed by SEM, and characterized by FT-IR, XRD and TGA. The optimum adsorption efficiency were achieved by a series of conditions optimization. The adsorption of Cu(II) by SA/DE@ZIF-8 conforms to the Langmuir adsorption model, and the theoretical maximum adsorption capacity is 599.07 mg/g. In summary, this study opens up a new strategy for the design of efficient and easily recycled ZIF-8 composite microspheres for water treatment.