Fabrication of magnetic Fe3O4@metal organic framework@covalent organic framework composite and its selective separation of trace copper

A novel magnetic composite, Fe3O4@metal organic [email protected] organic framework (Fe3O4@[email protected]), was first time prepared by solvothermal methods for selectively separation and preconcentration of Cu2+. The prepared Fe3O4@[email protected] composite was thoroughly characterized with XPS, TEM, XRD and FT-IR et al. With a high density of nitrogen- and oxygen-containing functional groups on the surface, the Fe3O4@[email protected] composite could efficiently extract and preconcentrate of Cu2+ ions in aqueous solutions, with a maximum Cu2+ adsorption capacity of 37.29 mg g−1 determined by fitting the adsorption curve to the Langmuir isotherm equation. The magnetic composite after adsorption of Cu2+ was readily separated with an external magnet, and the retained copper could be stripped by acetic acid, which can effectively catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 with the detection of UV–vis spectrophotometry. The detection limit of this platform for Cu2+ is 37.6 nM (n = 11), along with a RSD of 4.14% (0.2 μM, n = 13). It was validated by measurement of water samples and the comparison to graphite furnace atomic absorption spectrometry (GFAAS) was accomplished.