Enhanced Fenton catalytic degradation of methylene blue by the synergistic effect of Fe and Ce in chitosan-supported mixed-metal MOFs (Fe/Ce-BDC@CS).

Methylene blue (MB) is a refractory organic pollutant that poses a potential threat to the aquatic environment. Fenton reaction is considered a primrose strategy to treat MB. However, the traditional Fenton process is plagued by narrow pH application range, poor stability, and secondary pollution. To solve these problems, many Fenton-like catalysts including metal-organic frameworks (MOFs) have been prepared. Herein, a novel bimetallic MOF (Fe/Ce-BDC@CS) was prepared through simple adsorption for the effective removal of MB, where chitosan (CS) was used as the carrier. The degradation performance of Fe/Ce-BDC@CS (100 % within 20 min) was better than that of most reported monometallic MOFs. Moreover, Fe/Ce-BDC@CS exhibited good repeatability and its anti-interference performance of some inorganic ions was also remarkable. Column loading experiments showed that the removal efficiency of MB was still about 50 % over 155 h with a flowing speed of 0.30 L/h. Comparative analysis indicated that such excellent performances could be attributed to the synergistic effect between Fe and Ce. Furthermore, the results of quenching tests indicate that OH, O2-, and 1O2 contributed to MB degradation. In brief, Fe/Ce-BDC@CS has promising prospects in MB treatment, which can provide scientific references for the design and application of bimetallic MOFs.

Zheng Y ，Ran L ，Zhang X ，Zhu L ，Zhang H ，Xu J ，Zhao Q ，Zhou L ，Ye Z ... -  《-》

Highly efficient Fenton and enzyme-mimetic activities of NH(2)-MIL-88B(Fe) metal organic framework for methylene blue degradation.

He J ，Zhang Y ，Zhang X ，Huang Y ... -  《Scientific Reports》

Iron-copper bimetallic metal-organic frameworks for efficient Fenton-like degradation of sulfamethoxazole under mild conditions.

Iron and copper bimetallic MOF material (FexCu1-x(BDC)) as a novel Fenton-like catalyst was prepared by a simple solvothermal method, and its performances were evaluated in the catalytic degradation of sulfamethoxazole (SMX) in the presence of hydrogen peroxide. The results indicated that the FexCu1-x(BDC)/H2O2 system was highly effective for SMX degradation over a wide pH range (4.0-8.6). At initial solution pH of 5.6, the bimetallic Fe0.75Cu0.25(BDC) catalyst exhibited a 100% SMX (20 mg L-1) removal within 120 min, which was superior to the SMX removal efficiency over monometallic Fe(BDC) and Cu(BDC) catalysts. Combined with the physical-chemical characterization, the synergistic effect between Fe and Cu species were responsible for the efficient catalytic activity. Moreover, the Fe0.75Cu0.25(BDC) catalyst showed good reusability for SMX degradation. The possible reaction mechanism in FexCu1-x(BDC)/H2O2 system was also tentatively proposed. This work has not only suggested the potential of bimetallic FexCu1-x(BDC) catalysts in Fenton-like treatment of antibiotics, but also provided useful information to develop MOF-based catalysts for efficient environmental remediation.

Tang J ，Wang J 《-》

Structure-performance correlation guided cerium-based metal-organic frameworks: Superior adsorbents for fluoride removal in water.

Fluoride in the hydrosphere exceeds the standard, which could be critically hazardous to human health and the natural environment. The adsorption method is a mature and effective way to remove pollutants in water, including fluoride. In this study, we synthesized three kinds of cerium-based metal-organic frameworks (Ce-MOFs) with different structures and properties by modulating the organic ligands (i.e., trimesic acid (BTC), 1,2,4,5-benzenetetracarboxylic acid (PMA), and terephthalic acid (BDC)) via the solvothermal method. The adsorption kinetics of Ce-MOFs on fluoride well fit the pseudo second order model, and their adsorption isotherms also conform to Langmuir isothermal model. The thermodynamic study reveals that the adsorption process is a spontaneous endothermic reaction. The maximum saturated adsorption capacities of Ce-BTC, Ce-PMA, and Ce-BDC are 70.7, 159.6, and 139.5 mg g-1, respectively. Ce-MOFs have stable and excellent adsorption capacity at pH = 3-9. Coexisting anions (Cl-, SO42-, and NO3-) do not affect the performance of Ce-MOFs for fluoride removal. Moreover, Ce-MOFs also show their broad prospect as superior fluoride adsorbents because of their excellent performance and reusability in real water samples. Organic ligands have a remarkable influence on the defluoridation performance of Ce-MOFs. This work will provide a feasible idea for designing MOFs as superiors adsorbents for defluoridation.

Tang X ，Xia W ，Qu X ，Wang C ，Wang W ，Liang Y ，Zeng Y ，Xiong W ，Cheng M ，Song B ，Zhou C ，Zhao X ... -  《-》

Facile one-step synthesis of 3D honeycomb-like porous chitosan bead inlaid with MnFe bimetallic oxide nanoparticles for enhanced degradation of dye pollutant.

Developing a sustainable, efficient and recyclable heterogeneous Fenton-like catalyst is important to wastewater treatment. Herein, well-dispersed MnO2 and Fe3O4 nanoparticles inlaid in chitosan beads (MnO2-Fe3O4/CH) was firstly fabricated and employed in the degradation of methylene blue (MB). The bead was prepared via a facile one-step method by dropwise addition of chitosan-metal salt solution into alkaline solution. Comparing with monometallic chitosan beads (MnO2/CH, Fe3O4/CH) and naked MnO2-Fe3O4, MnO2-Fe3O4/CH displayed significantly higher activity for MB degradation with the assistance of hydrogen peroxide (H2O2), finally removing 96.8% MB under the optimal conditions (50 mg L-1 MB, 4.0 g L-1 catalyst, 30 g L-1 H2O2, pH = 7, 60 min). Based on a series of characterizations, the large surface area (60.1 m2 g-1), well-developed porosity (0.3 cm3 g-1), and intensified electron transport of MnO2-Fe3O4/CH consequently enhanced the catalytic performance via a synergistic effect. Because the specific porous structure of MnO2-Fe3O4/CH facilitated the adsorption/diffusion of reactants and exposure of active sites. Meanwhile, the electron transfer from Mn3+ to Fe3+ accelerated the Fe3+/Fe2+ cycle, which favored the production of dominant reactive species hydroxyl radical for MB degradation. Besides, the magnetic beads could be easily collected from the solution and reused for five times with a negligible leaching.

Yang J ，Ao Z ，Niu X ，Dong J ，Wang S ，Wu H ... -  《-》