Studied On Modification Of Metal Organic Framework MIL-101 And Removal Of Organic Pollutants

Metal-Organic frameworks（MOFs）bearing the excellent properties of high specific surface area,large pore volumes and abundant active sites,are promising precursors to fabricate highly efficient photocatalysts.Also,MOFs-derived porous carbon materials can be fabricated via simple carbonization of MOFs.The porous carbons inheriting features of MOFs simultaneously have high electron conductivities and stabilities,attracting wide attentions in the field of photocatalysis.Large band gaps of MOFs and MOFs-derived porous carbon materials,however,are difficult to be excited under visible light irradiation,leading to low photocatalytic performances.Accordingly,an effective strategy,introducing semiconductor materials into the catalyst systems,is frequently to be used.In this paper,several photocatalysts were developed through combining MOFs or MOFs-derived porous carbons with α-Fe₂O₃ to improve photocatalytic performances.Research contents are as follows:Firstly,the MIL-101（Cr）was successfully synthesized in this paper,and then a series ofα-Fe₂O₃（C）/MIL-101（Cr）composites photocatalysts were prepared by a hydrothermal method.X-ray diffraction（XRD）,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）results exhibited that phaseα-Fe₂O₃ in the composite was provided a small particle size compared to that of a pureα-Fe₂O₃.And,its specific surface area was significantly increased to 948.6 m²/g.Radical trapping experiment,band edge position analysis and electron spin resonance（ESR）measurements suggested that a Z-scheme structure may be formed betweenα-Fe₂O₃ and MIL-101（Cr）phases.High resolution transmission（HRTEM）and X-ray photoelectron spectroscopy（XPS）results further proved that the both phases in the composite exactly had interfacial interaction,indicating the formation of a direct Z-scheme structure.Under visible light irradiation,10mg of theα-Fe₂O₃（0.3）/MIL-101（Cr）composite photocatalysts realized the complete degradation of carbamazepine（CBZ）within 180 min.Secondly,based on the above research results,α-Fe₂O₃/MIL-101（Cr）/NCDs composite photocatalysts were prepared by the introducing of carbon quantum dots（NCDs）into the catalystα-Fe₂O₃/MIL-101（Cr）.The results of photoluminescence（PL）,UV-vis diffuse reflectance spectroscopy（UV-vis DSR）and ESR showed that the introduction of NCDs accelerated the separation and transfer of photogenerated electron hole pairs,inhibited the recombination of photogenerated carriers,broadened the light absorption range of the composite,and promoted the improvement of the photocatalysis performance.Under visible light irradiation,CBZ can be completely degraded inside 60minutes by adding 10 mg ofα-Fe₂O₃（0.3）/MIL-101（Cr）/NCDs（2）composite.Finally,porous carbon material Cr@C was prepared by directly calcining of MIL-101（Cr）,and successively a series ofα-Fe₂O₃（C）/Cr@C composite photocatalysts were obtained by a hydrothermal method.The physico-chemical properties of the samples illustrated that a p-type semiconductor Cr2O3 phase was existed in the Cr@C-based porous carbon,which combined with the n-type semiconductorα-Fe₂O₃ to form a p-n heterojunction,effectively transferring the photogenerated carriers.Under visible light irradiation,adding 6 mg ofα-Fe₂O₃（0.3）/Cr@C900 composite photocatalysts into a photodegradation system,CBZ solution was completely degraded within 180 min.