The preparation of Ag/ZIF-8@ZIF-67 core-shell composites as excellent catalyst for degradation of the nitroaromatic compounds

The high effective Ag/ZIF-8@ZIF-67 core-shell composite was fabricated by a convenient strategy and applied in the reduction of 4-nitrophenol. The obtained samples were fully characterized by transmission electron microcopy (TEM), element mapping, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and the like. Catalytic experiments showed that the Ag/ZIF-8@ZIF-67 exhibit superior catalytic activity in the reduction of 4-nitrophenol and another two nitroaromatic compounds. The apparent rate constant (K-app) and the conversion frequency (TOF) of Ag/ZIF-8@ZIF-67(0.4) for 4-nitrophenol were 12.22 x 10(-3) s(-1) and 5.611 min(-1), respectively, and preserved high catalytic performance after four cycles. The catalytic activity of Ag/ZIF-8@ZIF-67 was significantly increased compared to Ag/ZIF-8, which was mainly attributed to the high specific surface area of ZIF-8@ZIF-67, the synergy of ZIF-8 core and ZIF-67 shell and the restriction of pores to Ag NPs.