| The method of using light to reduce carbon dioxide into usable carbon-containing products is considered one of the most promising solutions to the fossil fuel energy crisis and reducing carbon dioxide emissions.In recent years,metal-organic frameworks(MOFs)have become a popular object of research in the field of CO2 photocatalysis due to their unique electronic band structure,excellent CO2 adsorption capacity,and adjustable light absorption ability.This paper focuses on the design and synthesis of MOF-based photocatalysts,specifically the design,synthesis,and efficiency of Zr-based MOFs-UiO-66 composite materials for photocatalytic CO2 reduction.The study emphasizes the combination of UiO-66 with two types of molybdenum-based materials,Mo2C and MoO3-x,to investigate the enhancement of UiO-66’s photocatalytic activity through the construction of heterojunctions.The study also examines the performance and mechanism of the composite material for photocatalytic CO2 reduction in detail.This research provides new insights for the rational design of UiO-66 photocatalysts and provides theoretical and technical support for the application of photocatalytic technology in greenhouse gas management.The research is divided into two parts:(1)The first part uses a solvothermal method to in situ load UiO-66 nanoparticles onto the surface of Mo2C to successfully construct a Mo2C@UiO-66 heterojunction composite catalyst.The composite material exhibits excellent photocatalytic CO2 reduction performance.Compared to single materials,UiO-66 and Mo2C,the composite material has the advantages of high specific surface area of UiO-66 and high visible light utilization rate of Mo2C.By improving the specific surface area and enhancing electron conductivity,the CO2 adsorption and activation capacity is greatly improved.The results of photocatalytic CO2 reduction show that the highest yield of CO produced by the Mo2C@UiO-66 composite material can reach 31.16 μmol·h-1·g-1,which is 13.9 times higher than that of UiO-66 and 19 times higher than that of Mo2C.A series of characterization results indicate that the Mo2C@UiO-66 composite material forms a Z-type heterojunction,which is conducive to the separation and transfer of photoinduced carriers,further improving the efficiency of photocatalytic reduction.This section provides new ideas for systematically exploring the effect of heterojunctions on CO2 reduction to CO,and also expands the application of Z-type heterojunctions in the photocatalytic reduction of CO2.(2)The second part mainly studies the synergistic effect of oxygen vacancies(OVs)and heterojunction catalysts on photocatalytic CO2 reduction to CO.By using a hydrothermal method to wrap UiO-66 on the surface of MoO3-x with a large number of oxygen vacancies,a composite material with both high specific surface area and high visible light utilization rate is obtained,which improves the CO2 photocatalytic reduction efficiency by introducing oxygen vacancies.The results show that the sample with oxygen vacancies(UiO-66@MoO3-x)exhibits much better performance in the photocatalytic reduction of CO2 than the materials MoO3-x and UiO-66 before combination,and the best material performance is obtained by adjusting the ratio of the composite material.The CO production rate of MoO3-x@UiO-66 photocatalytic reduction can reach up to 173.6 μmol·h-1·g-1,which is 44.5 times higher than that of UiO-66 and 40.6 times higher than that of MoO3-x.Characterization results indicate that the improvement in the performance of the composite catalyst is mainly due to the presence of a large number of oxygen vacancies,which enhances the material’s ability to capture visible light and lowers the reduction potential of CO2,providing abundant active sites for photons to be fully utilized and increasing its photocatalytic activity.In addition,the composite material forms a Z-type heterojunction,further promoting the separation and transfer of electrons and enhancing the visible light absorption capacity of the material. |
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