ABSTRACT
Expression of Concern for 'Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO' by Reda S. Salama et al., RSC Adv., 2021, 11, 4318-4326, https://doi.org/10.1039/D0RA09970H.
ABSTRACT
In the present work, Mn3O4 was prepared by various methods and successfully loaded with metallic Au nanoparticles reduced by hydrazine hydrate using microwave irradiation (MWI) method. The surface morphology and composition of the prepared samples were characterized with X-ray diffraction (XRD), N2 adsorption-desorption, temperature programmed reduction (H2-TPR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The experimental results showed that no significant changes in some textural and structural properties of the samples due to preparation method or Au nanoparticles deposition. While the surface composition and reducibility of the samples were greatly affected by preparation method and Au deposition. The CO oxidation reaction over the samples was selected as a model reaction to study the relation between surface properties of the samples and their catalytic performance. The results showed that a direct proportionality exists between the reducibility and the CO oxidation activity of catalysts. The kinetic study of the reaction showed that the reaction is first order. Moreover, the samples exhibited good stability in CO oxidation at 100% conversion for around 30â h under the reaction conditions.
Subject(s)
Gold , Metal Nanoparticles , Catalysis , Microwaves , TemperatureABSTRACT
Successful monometallic and bimetallic metal-organic frameworks with different Co/Mn ratios have been synthesized under solvothermal conditions. The as-synthesized MOFs followed by deposition of Pd nanoparticles with 0.5 to 7 wt%. The XRD, BET, SEM, TEM, EDAX and FT-IR characterization results reveal that bimetallic MOFs and Pd nanoparticles were finely dispersed on the prepared MOFs surfaces. XRD results confirm the formation of the desire MOFs and show the high degree of dispersion of Pd nanoparticles. TEM images show that Pd nanoparticles are nano-sized with almost uniform shape. EDAX shows that Pd nanoparticles successfully loaded on Co0.5-Mn0.5-MOF-74 catalyst. CO oxidation as a model reaction was then used to assess the catalytic performance of the prepared catalysts. The catalytic activity results show enhancement in the catalytic activities of monometallic MOFs after introducing another metal in the same framework and show an excellent improvement in CO conversion after loading with Pd nanoparticles. Furthermore, the samples that contain Pd nanoparticles exhibits higher catalytic activities which raised with increasing the content of Pd nanoparticles.
ABSTRACT
The drug resistance of bacteria is a significant threat to human civilization while the action of antibiotics against drug-resistant bacteria is severely limited owing to the hydrophobic nature of drug molecules, which unquestionably inhibit its permanency for clinical applications. The antibacterial action of nanomaterials offers major modalities to combat drug resistance of bacteria. The current work reports the use of nano-metal-organic frameworks encapsulating drug molecules to enhance its antibacterial activity against model drug-resistant bacteria and biofilm of the bacteria. We have attached rifampicin (RF), a well-documented antituberculosis drug with tremendous pharmacological significance, into the pore surface of zeolitic imidazolate framework 8 (ZIF8) by a simple synthetic procedure. The synthesized ZIF8 has been characterized using the X-ray diffraction (XRD) method before and after drug encapsulation. The electron microscopic strategies such as scanning electron microscope and transmission electron microscope methods were performed to characterize the binding between ZIF8 and RF. We have also performed picosecond-resolved fluorescence spectroscopy to validate the formation of the ZIF8-RF nanohybrids (NHs). The drug release profile experiment demonstrates that ZIF8-RF depicts pH-responsive drug delivery and is ideal for targeting bacterial disease corresponding to its inherent acidic nature. Most remarkably, ZIF8-RF gives enhanced antibacterial activity against methicillin-resistant Staphylococcus aureus bacteria and also prompts entire damage of structurally robust bacterial biofilms. Overall, the present study depicts a detailed physical insight for manufactured antibiotic-encapsulated NHs presenting tremendous antimicrobial activity that can be beneficial for manifold practical applications.
