Layer-by-Layer Fabrication of Core–Shell Fe3O4@UiO-66-NH2 with High Catalytic Reactivity toward the Hydrolysis of Chemical Warfare Agent Simulants

Detoxifying materials against chemical warfare agents (CWAs) and their simulants are highly desired for proper handling of contamination by and destruction of CWAs. Herein, we report a facile layer-by-layer fabrication of core–shell Fe 3 O 4 @UiO-66-NH 2 and its application in fast degradation of CWA simulants. The Fe 3 O 4 @UiO-66-NH 2 composite was prepared through a layer-by-layer epitaxial growth strategy, by alternately immersing Fe 3 O 4 nanoparticles in ethanol solutions of a metal node [Zr 6 O 4 (OH) 4 ] 12+ precursor and organic linkers [NH 2 -BDC, 2-aminoterephthalic acid], respectively, and separating using a magnet. As confirmed by characterization results, the Fe 3 O 4 @UiO-66-NH 2 composites with 24.4 μmol/g Zr 6 node content showed a well-defined core–shell structure as well as good thermal and chemical stability. These core–shell magnetic metal–organic frameworks (MOFs) were further tested in the catalytic hydrolysis of dimethyl-4-nitrophenyl phosphate (a nerve agent simulant) and demonstrated 36 times higher catalytic activity than the UiO-66-NH 2 powder due to their highly defective surface, high percentage of MOFs on the surface, and their rich mesoporous structure. Since magnetism was retained after the coating of MOFs, Fe 3 O 4 @UiO-66-NH 2 could be easily recovered and reused after catalysis.