The persulfate activation-based advanced oxidation process (PS-AOP) is an important technology in wastewater purification. Using metal-organic frameworks (MOFs) as heterogeneous catalysts in the PS-AOP showed good application potential. Considering the intrinsic advantages and disadvantages of MOF materials, combining MOFs with other functional materials has also shown excellent PS activation performance and even achieves certain functional expansion. This Review introduces the classification of MOFs and MOF-based composites and the latest progress of their application in PS-AOP systems. The relevant activation/degradation mechanisms are summarized and discussed. Moreover, the importance of catalyst-related interfacial interaction for developing and optimizing advanced oxidation systems is emphasized. Then, the interference behavior of environmental parameters on the interfacial reaction is analyzed. Specifically, the initial solution pH and coexisting inorganic anions may hinder the interfacial reaction process via the consumption of reactive oxygen species, affecting the activation/degradation process. This Review aims to explore and summarize the interfacial mechanism of MOF-based catalysts in the activation of PS. Hopefully, it will inspire researchers to develop new AOP strategies with more application prospects.
A self-templated strategy was adopted to design hollow Co3O4/MO3 (M = Mo, W) mixed-metal oxides via the Mo or W doping of ZIF-67, and subsequent pyrolysis under an atmosphere of air at a low temperature of 450 °C. The hollow Co3O4/MO3 (M = Mo, W) mixed-metal oxides displayed tunable oxidase-like and peroxidase-like activities able to efficiently catalyze the oxidation of TMB to generate a deep blue color in the absence or presence of H2O2. Relative to that of the un-doped Co3O4, the oxidase mimic activity of the Mo-doped Co3O4 increased to 1.3 to 2.1-fold, while its peroxidase mimic activity increased to 7.1 to 19.9-fold, depending on different Mo doping amounts. The oxidase mimic activity of the W-doped Co3O4 increased to 2.1 to 2.3-fold, while its peroxidase mimic activity increased to 4.8 to 5.9-fold, depending on the different W doping amounts. The Mo- and W-doped Co3O4 nanohybrid exhibited both higher O2 and H2O2 activating capability, and their H2O2 activating capacity was superior to the O2 activating capability. Furthermore, the Mo- and W-doped Co3O4 nanohybrids exhibited similar O2 activating abilities, while the Mo-doped one displayed a higher H2O2 activating capability than the W-doped one. The discrepant peroxidase-like nature of Mo- and W-doped Co3O4 nanohybrids is likely attributed to their different catalytic mechanisms. The peroxidase-like activity of Mo-doped Co3O4 is highly related to the ˙OH free radical, while that of W-doped Co3O4 is likely ascribed to the electron transfer between TMB and H2O2. The Km values of Co3O4/MoO3 for TMB and H2O2 were 0.0352 mM and 0.134 mM, which were 3.2- and 1.9-fold lower than that of pure Co3O4, respectively. A Co3O4/MoO3-based colorimetric platform was developed for the determination of H2O2 in the 0.1-200 μM range, with a limit of detection of 0.08 μM (3σ). Based on the thiocholine (TCh) inhibition of the excellent peroxidase-like activity of Co3O4/MoO3 and the TCh generation via acetylcholinesterase (AChE) catalyzed hydrolysis of acetylthiocholine chloride (ATCh), the colorimetric platform was extended to screen AChE activity and its inhibitor.
Direct pyrolysis of a Prussian blue analogue produced FeCo@NC with high and stable peroxidase-like activity, which catalyzes luminol oxidation by H2O2 to generate strong CL emission, and this finding results in a new CL biosensor for glucose.
Rational design of high-performance nanozyme is of great significance for sensing applications. Here, N-doped carbon nanocages containing Co-Nx active sites (CoNx-NC) were fabricated by simple acid etching of Co@NC, which is the product of Co–Co Prussian blue analogues carbonized in an N2 atmosphere. Both optimized Co@NC-650 and CoNx-NC-650 exhibit catalase- and oxidase-like properties. They rapidly decompose H2O2 into O2 and oxidize colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product. This enables them with no peroxidase-like activity. The oxidase-like activity of CoNx-NC-650 is 3.9 times that of unetched Co@NC-650. The acid treatment dissolves Co nanoparticles generated during carbonization, forming extra mesoporous structures and increasing the exposure of more Co-Nx active species. The Michaelis–Menten constant for CoNx-NC-650 with a TMB substrate is 0.186 mM, which is 3.2 times lower than that of oxidase-mimicking CeO2 nanoparticles, suggesting a higher affinity to TMB. Given its excellent oxidase-like activity, the CoNx-NC-650 was used to sensitively and selectively determine acetylcholinesterase (AChE) activity based on thiocholine inhibition of the TMB color reaction. Thiocholine is produced via hydrolysis of acetylthiocholine catalyzed by AChE. The colorimetric biosensor has a linear response to AChE over 0.6–800 mU L–1 concentration range and a detection limit (3σ) of 0.2 mU L–1. The assay was successfully applied to determine AChE activity in biological samples.
Here, we reported a facile strategy to prepare Co nanoparticles (NPs) encapsulated in two-dimensional (2D) N-doped porous carbon nanosheets (2D Co/NC) via pyrolyzing Zn/Co bimetallic metal–organic framework (MOF) nanosheets, which were prepared in aqueous solution. The successful synthesis of Zn/Co bimetallic MOF nanosheets and 2D Co/NC was demonstrated by various characterization techniques. The optimized 2D Co0.6/NC-700 and three-dimensional (3D) Co0.6/NC-700 show catalase- and oxidase-like activities. They can break down H2O2 into O2 and oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product, while the former displays superior performance to its 3D Co0.6/NC-700 aggregated nanoparticles. Specifically, the oxidase-mimicking activity and catalase-like activity of 2D Co0.6/NC-700 are 1.64-fold and 6.9-fold those of 3D Co0.6/NC-700, respectively. Relative to 3D Co0.6/NC-700 aggregates, the improvement of the catalytic activity of 2D Co0.6/NC-700 is likely ascribed to its 2D leaf-like structure with more accessible dispersed active sites and the interaction between Co NPs and N-doped carbon nanosheets. 2D Co0.6/NC-700 displayed superior oxidase-like activity with a low Michaelis–Menten constant (Km) of 0.35 mM. Interestingly, in the presence of both acetylcholinesterase (AChE) and acetylthiocholine (ATCh), the oxidase-like activity was suppressed because of the generation of thiocholine, which led to the fading of the TMB color reaction. On this basis, a colorimetric assay was developed for the determination of AChE activity. 2D Co0.6/NC-700 displayed excellent detection performance in AChE activity, with a linear detection range of 0.0002–0.8 U L–1 and a low detection limit of 0.0002 U L–1. Remarkably, the method showed good selectivity to AChE, and other coexisting substances had minor interference. The method was satisfactorily utilized to determine the AChE activity in real samples.
A 2D Fe-BTC nanosheet was preparedviaa cation exchange route. Its peroxidase-like activity is 2.2 times that of 3D MIL-100(Fe) due to highly accessible surface active sites. This is helpful for substrate contact with the catalyst during the catalytic reaction.
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