Preparation And Catalytic Performances Of Boron And Iron Doped Carbon Nitrde Materials For Oxidative Removal Of RhB And CO₂ Cycloaddition Reactions

In this thesis,graphite layered carbon nitride?g-C₃N₄?with and without support,and CN-C-CN/SBA-15 were prepared,and their catalytic performances for oxidative degradation of Rodamine B and CO₂ cycloaddition reactions were investigated.Fe-containing carbon nitrides?Fe-CN?prepared with various CN precursors,including dicyandiamide,melamine,guanidine hydrochloride and urea,were prepared and used to catalyze the Rhodamine B oxidation,with H₂O₂ as oxidant.Characteristic results showed that the Fe-CN samples with different compositions,properties and thus catalytic performances would be obtained if different CN precursors are used.Fe-CN prepared from dicyandiamide contains mainly the CN phase and has suitable amounts of surface iron species,exhibits the best activity;while that prepared from urea contains mainly the Fe₂O₃ phase and has big particle size,exhibits the worst activity.Contrasting experiments conducted under light irradiation,with a supported Fe/CN_D catalyst,and that using a washed catalyst,confirm that the surface iron species is the main active phase of the reaction.To exploit fully the catalytic performances of Fe-CN,we impregnated it on high-surface-area mesoporous silica.The catalytic performances for RhB oxidation was analyzed by controlling the amount of Fe-CN and the amount of Fe dopant,as well as the type of silicas,including SBA-15,MCM-41 and KIT-5.The results showed that the optimum conditions are obtained using SBA-15 as support,Fe-CN loading of 72%,and Fe doping of 20%,that is,72%Fe₂-CN/SBA-15,at which the RhB conversion reaches to 81.6%.Also,combining carbon dioxide with epoxies to synthesize cyclic carbonate through cycloaddition under solvent-free conditions is an eco-friendly way to apply CO₂ in environmental science and green chemistry.In this work,boron doped graphitic carbon nitride?BCN?was supported on high-surface-area ordered mesoporous silica SBA-15,and the resultant BCN/SBA-15 performed well in the reaction of cycloaddition of CO₂ and styrene oxide?SO?,of which the conversion and selectivity was over 95%under solvent-free conditions.Additionally,the catalyst showed high activity even after cycle usage.It was due to the doping of B atoms made BCN possess dual active acid and base sites,which could respectively activated SO and CO₂.We prepared a SBA-15 supported CN-C-CN catalyst,and tested its catalytic performances for cycloaddition of CO₂ and styrene oxide to yield styrene carbonate,using N,N-Dimethylformamide?DMF?as solvent.Results showed that the catalyst can catalyze the reaction efficiently,with the conversion of 75%?...