Catalytic oxidation of vinyl chloride over Co-Ce composite oxides derived from ZIF-67 template:Effect of cerium incorporation

Transition metal oxides are regarded as an economical and efficient catalytic alternate for catalytic oxidation of volatile organic compounds(VOCs)emissions.The morphological decoration and the incorporation of extrinsic metals were demonstrated to be effective strategies for achieving noticeable catalytic improvement.In this work,a novel Co-Ce composite oxides catalyst was obtained by the pyrolysis of ZIF-67 template with the impregnation of certain cerium cations(denoted as ZIF-CoCe).Compared with the reference Co-Ce composite oxides by the sol-gel(denoted as SG-CoCe)and physical mixing(denoted as MIX-CoCe)methods,ZIF-CoCe delivers significantly higher catalytic activity for vinyl chloride oxidation,which are demonstrated to be closely related with its superior redox capacity,more abundance of surface active Co^(3+)sites and adsorbed active oxygen species from oxygen vacancies.In addition,the unique cage-like morphological feature of the Co-based catalysts derived from ZIF-67 template plays a crucial function in kinetically facilitating the mass transfer of catalytic reaction and promoting the catalytic VC oxidation activity.With regard to in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTs)analysis,enol and carboxylic acid species are identified to be the key organic intermediates during catalytic vinyl chloride oxidation.

Enhanced antibacterial activity of silica nanorattles with ZnO combination nanoparticles against methicillin-resistant Staphylococcus aureus

Silica nanorattles(SNs) with zinc oxide(ZnO) combination nanoparticles are reported to inhibit methicillin-resistant Staphylococcus aureus(MRSA) for the first time. SNs loaded with ZnO nanoparticles,which can produce free radicals, can cause severe damage to bacteria. ZnO nanoparticles not only provide free radicals in the combined nanostructures, which can inhibit the growth of bacteria, but also form nanorough surfaces with an irregular distribution of spikes on the SNs, which can enhance their adhesion to bacteria. Nanorough silica shell surfaces maintain the high activity and stability of small-sized ZnO nanoparticles and gather ZnO nanoparticles together to enhance production, which improves the efficiency of free radicals against the cytomembranes of bacterial cells. The enhanced adhesion of ZnO@SN nanoparticles to MRSA cells shortens the effective touching distance between free radicals and MRSA, which also improves antibacterial activity. As we expected, the ZnO@SN nanoparticles exhibit a better antibacterial effect than free ZnO nanoparticles against MRSA in vitro and in vivo. We also demonstrate that SNs loaded with ZnO nanoparticles can accelerate wound healing in MRSA skin inflammation models. This method of multilevel functionalization will be potentially applicable to the antibacterial field.

Screening performance of methane activation over atomically dispersed metal catalysts on defective boron nitride monolayers:A density functional theory study

Methane(CH_(4))controllable activation is the key process for CH_(4)upgrading,which is sensitive to the surface oxygen species.The high thermal conductivity and superb thermal stability of the hexagonal boron nitride(h-BN)sheet makes a single transition metal atom doped hexagonal boron nitride monolayer(TM-BN)possible to be a promising material for catalyzing methane partial oxidation.The performances of 24 TM-BNs for CH_(4)activation are systematically investigated during the CH_(4)oxidation by means of first-principles computation.The calculation results unravel the periodic va riation trends for the stability of TM-BN,the adsorption strength and the kind of O_(2)species,and the resulting CH_(4)activation performance on TM-BNs.The formed peroxide O_(2)^(2-)of which the O-O bond could be broken and O-anions are found to be reactive oxygen species for CH_(4)activation under the mild conditions.It is found that the redox potential of TM center,including its valence electron number,coordination environment,and the work function of TM-BN,is the underlying reason for the formation of different oxygen species and the resulting activity for CH_(4)oxidative dehydrogenation.