Facet Design And Photocatalytic Reduction Of Carbon Dioxide Of Metal-Organic Frameworks

In recent years,high concentrations of carbon dioxide in the environment have contributed to global warming.Selecting a suitable catalyst and using visible light to reduce carbon dioxide to high value-added products is an effective way to convert carbon dioxide.In this paper,a series of metal-organic framework catalysts were prepared to explore the dependence of photocatalytic reduction of carbon dioxide on its exposed planes.Combined with density functional theory and other methods,the relevant mechanism of the influence of MOFs on the performance of photocatalytic carbon dioxide was systematically discussed.This thesis mainly includes the following aspects:1.By changing the temperature and time of the solvothermal reaction,the {110} plane of NH2-MIL-125(Ti)ultrathin nanosheet was successfully synthesized.The ultra-thin structure is conducive to exposing more active sites in the photocatalytic process,making it easier to transfer photogenerated carriers,and significantly inhibiting electron-hole recombination.Compared with several other three-dimensional NH2-MIL-125 materials that expose different facets,ultrathin nanosheets with {110} facet show higher photocatalytic CO2 reduction efficiency.Density functional theory proves that the outer layer of the nanosheet has more Ti atoms that can directly participate in the catalytic reaction,and these metal catalytic sites are located at the location of photoexcited electrons,thereby significantly enhancing the photocatalytic activity.Experimental and theoretical results jointly confirm the relationship between photocatalytic reduction of carbon dioxide and NH2-MIL-125 ultrathin nanosheets.2.A room temperature stirring method was designed to prepare a series of HKUST-1 containing different facets,and the relationship between the photocatalytic activity of CO2 reduction reaction and the exposed plane was studied.By changing the concentration of the surfactant cetyltrimethylammonium bromide,a series of HKUST-1 materials exposed to{100},{111} and {100}/{111} planes were successfully synthesized.The results of photocatalytic reduction of CO2 show that HKUST-1 with co-exposed facets {100}/{111}has higher photocatalytic efficiency in photocatalytic reduction of CO2.It is worth noting that in addition to the C1 product,the catalyst also produces a highly selective C2+product C2H4.3.Ag nanoparticles were uniformly distributed to HKUST-1 materials with different planes by reduction method,and HKUST-1-Ag composite catalysts with different morphologies were obtained.In applications of visible photocatalytic reduction of carbon dioxide,the most excellent photocatalytic reduction of carbon dioxide performance can be obtained by co-exposure of {100}/{111} planes.It is revealed that the catalytic activity of the composite is mightily dependent on the plane of the catalysts.The test results show that the close contact between Ag NPs and HKUST-1 can effectively accelerate the charge transfer in the sample and inhibit the electron-hole recombination,thereby improving the photocatalytic activity.