Construction And Catalytic Properties Of Transition Metals And Their Carbides @ Porous Carbon Composites

With the rapid development of industry,environmental water pollution is becoming more and more serious,especially the wastewater containing aromatic organic pollutants poses a serious threat to human health,so it is imperative to find efficient water treatment technology.At present,microwave catalysis technology has become a new technology for purifying organic wastewater because of its outstanding characteristics of fast catalytic rate,high activity,short reaction time and treatment of biodegradable organic pollutants.In addition,the direct catalytic reduction of toxic pollutants to nontoxic intermediates is also a very promising strategy.At the same time,it is necessary to find a catalyst with high catalytic activity,low preparation cost and easy recovery.In this work,a series of porous carbon-coated transition metals and their carbide composites were derived from metal-organic frameworks,using to microwave synergistic catalytic oxidation of antibiotics?Lomefloxacin,Ciprofloxacin?and direct catalytic reduction of p-nitrophenol.?1?CoZn-MOF as precursor derived to construct a novel 1D-2D hierarchical structure consisting of Co/Co₃ZnC nanoparticle-limited domains on carbon nanosheets grafted with nitrogen-doped carbon nanotubes?Co/Co₃ZnC@NCNTFs?.The morphology,size and structure of the materials were characterized by XRD,SEM,TEM,TGA,Raman,FTIR and XPS.At the same time,the influence of the precursor solvent and calcination temperature on the catalytic effect was investigated.The experimental results showed that:Co/Co₃ZnC@NCNTFs?ZIF-0/1-700N?is the ideal catalyst.LOM(50 mL,10 mg·L^-1)degradation rate reached 96.5%under the condition of catalyzer addition 40 mg,microwave radiation 7 min,microwave power700 W.The mass spectrometry analysis showed that the LOM was gradually decomposed and eventually mineralized into inorganic small molecules such as H₂O,CO₂,NO₃^-and F^-.The process conformed to the pseudo-first-order model with a rate constant of 0.314 min^-1.The mechanism of MW/Co/Co₃ZnC@NCNTFs synergistic catalytic degradation of LOM was studied through free radical capture experiments and ESR.The results showed that holes,superoxide radicals and hydroxyl radicals were the main active substances produced by the process.Based on the plasmon resonance effect,the possible catalytic reaction mechanism of MW/Co/Co₃ZnC@NCNTFs is speculated.The constructed Co/Co₃ZnC@NCNTFs in the presence of NaBH₄ can efficiently reduce 4-NP directly to 4-AP,demonstrating excellent catalytic reduction performance.HPLC analysis confirmed that 4-NP was successfully reduced to 4-AP in a short time.The reduction process conforms to the quasi-first-order kinetic model and the rate constant is 0.679 min^-1.At the same time,the catalytic oxidation and reduction performance of the Co/Co₃ZnC@NCNTFs was not significantly reduced after four times of reuse,showing excellent structural stability and reuse.?2?Fe-MOF as precursor derived to construct a novel sea Cucumber-like 3D hierarchical structure consisting of Fe/Fe₃C nanoparticle-limited domains on nanorods grafted with nitrogen-doped carbon nanotubes?Fe/Fe₃C@NCNTs?.XRD and SEM were used to characterize the morphology,size,and structure of the materials.Experimental results show that:CIP(50 mL,10 mg·L^-1)degradation rate can reach more than 90%under the condition of microwave radiation 10 min,microwave power 700 W.The degradation process was in accordance with the quasi-first-order kinetic model and the rate constants were 0.253 min^-1.The above results show that microwave synergistic transition metals and their carbides@porous carbon composites catalyze the degradation of pollutants in wastewater,which has the advantages of simple and easy recovery,short reaction time and high degradation efficiency compared with other conventional methods.