Halonitrophenols (HNPs) are an emerging type of aromatic disinfection byproduct, with detected concentrations of ∼nmol L−1 in source water and drinking water. Currently, there are no standard methods for identifying HNPs, and most of the reported methods are time-consuming and equipment-dependent. A core–shell metal–organic framework (MOF) based electrochemical sensor (Ag/ZIF-8@ZIF-67) capable of detecting 2,6-dichloro-4-nitrophenol (2,6-DCNP) is reported in this study. The electrochemical sensor obtains the concentration of 2,6-DCNP by detecting the peak current passing through the sensor. In this sensor, Ag nanoparticles (AgNPs) play a key role in electrochemical sensing by reducing nitro groups via electron transfer, and porous structure with a large surface area is offered by ZIF-8@ZIF-67. The cyclic voltammetry (CV) response of Ag/ZIF-8@ZIF-67 was found to be approximately 1.75 times and 2.23 times greater than that of Ag/ZIF-8 and Ag/ZIF-67, respectively, suggesting an ideal synergistic effect of the core–shell structures. The Ag/ZIF-8@ZIF-67 sensor exhibited exceptional sensitivity to 2,6-DCNP, exhibiting a broad linear response range (R2 = 0.992) from 240 nmol L−1 to 288 μmol L−1 and a low detection limit of 20 nmol L−1. Furthermore, the sensor exhibited good anti-interference for isomers and common distractors in water, excellent stability and reproducibility, and high recovery in actual water samples. Our reported sensor gives a novel strategy for sensitive, selective, and in situ detection of 2,6-DCNP in practical analysis.
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 × 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.
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