Zhendong Fu,Feng Guo,Jiahe Qiu,Runchi Zhang,Mingxu Wang,Liping Wang
2-Methylimidazole (MIM) is a classic organic ligand that shows excellent thermal stability and chemical robustness and is widely used in ZIFs. Recently, transformations of MOFs have been realized by using metals or ligands. In this study, we propose a new strategy—adjusting MIM by extending the alkyl chain length —to change the properties of related MOFs. Furthermore, we used copper as the metal core to replace zinc to mimic the active sites of laccases (electron transfer between copper and imidazole ring). As a result, the nanostructures transformed from nanoleaves to nanovesicles, which changed the Cu(II)/Cu(I) ratio from 3.7 to 1.7, as well as the lattice constant (decreased the diffraction angle) and enzyme-like activity (inhibition). In addition, we revealed that superoxidase anions were the main factors responsible for its laccase-like activity. We applied it to detect and discriminate phenolics. Laccase-mimicking activity was best at pH 7.0. When compared to protein laccase, the Cu-MeIm nanozyme had a greater Vmax at the same mass concentration. It was used to identify and distinguish phenolics. In the presence of Cu-MeIm nanozymes, the linear range is 0.1–2 mM and the detection limit of 2,4-DCP is 0.034 mM.
Chengfang Zhang,Jingchun Tang,Feilong Gao,Chen Yu,Song Li,Honghong Lyu,Hongwen Sun
The defects of easy agglomeration and oxidation of nano zero valent iron (nZVI) limit its large-scale application in industry, especially in the field of environmental remediation. In this study, the iron nanoparticles encapsulated by graphene nano-shells which anchored on the surface of carbon substrate (nZVI@gBC) were synthesized by a one-step carbothermal reduction method aided by Tetrahydrofuran. When the mass ratio of carbon source to iron source is 2:3 and the carbothermic reduction temperature is 700 °C, stabilized nZVI @gBC can be successfully synthesized with a high iron loading rate of 32.5%. The multilayer graphene shell can effectively prevent the rapid passivation and agglomeration of the nZVI core, and the electronic interaction between the iron nanoparticles core and the graphene carbon shell further enhances the catalytic activity and stability of nZVI@gBC. Therefore, due to the unique structure of graphene nano-shells, nZVI@gBC can be stably stored in the air for more than 80 days. In addition, nZVI@gBC exhibited superior catalytic activity in the experiment of removing 2,4-dichlorophenol (2,4-DCP) in groundwater as a persulfate activator. Notably, both the electron paramagnetic resonance (EPR) and quenching tests showed that SO 4 •− , •OH, O 2 •− and 1 O 2 were both involved in the degradation process of 2,4-DCP, and SO 4 •− were the major active species. Simultaneously, three possible degradation pathways of 2,4-DCP were deduced by GC/MS, which were caused by dechlorination, dehydrogenation or carbon–carbon bond cleavage under the attack of SO 4 •− , •OH, O 2 •− and 1 O 2 . Besides, nZVI@gBC can use the dissolved oxygen in the liquid to generate hydroxyl radicals to effectively remove 2,4-DCP without persulfate. This kind of multifunctional nZVI@gBC may become a promising iron-carbon catalyst for large-scale applications in the field of environmental remediation.
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