Preparation Of Metalloporphyrin/TiO₂ Composites And Photocatalytic Performance For CO₂ Reduction

With the excessive development and use of fossil energy such as coal,oil and natural gas,greenhouse gas emissions such as CO2 have increased rapidly,triggering global climate change and energy crisis.Faced with the growing problem of energy shortage and environmental degradation,how to efficiently develop renewable solar energy has become a hot spot of current research.In photocatalytic technology,the use of semiconductors as catalysts to convert CO2 into high value-added dyes under the driving of solar energy is one of the effective measures to solve energy and environmental problems.Due to its outstanding catalytic activity,TiO2 is stable in physicochemical properties,non-toxic and inexpensive,and is widely used in research.However,due to the wide band gap of TiO2,low utilization rate of light energy,and easy agglomeration,it limits its wider application.Metalloporphyrins contain a macrocyclic conjugated structure and a high absorption capacity for visible light.The metal organic framework(MOF)has a large specific surface area and various structural functions and is widely used for photocatalysis.In this thesis,metal porphyrin was used as sensitizer and ligand in MOF structure to prepare composite catalyst with TiO2,respecitively.The photocatalytic activities of CO2 reduction of composites were characterized and their possible mechanism was discussed.This work provides useful reference and inspiration for the further development of metalloporphyrin.The research contents are as follows:(1)CuTCPP/P25m photocatalytic CO2 reduction:the surface of commercial P25 was hydroxylated(P25m)by hydrothermal method to make the surface contain more hydroxyl groups.The porphyrin sensitized TiO2 composite material CuTCPP/P25m was obtained by recombination of copper porphyrin(CuTCPP)with TiO2.The photocatalytic reaction mechanism was discussed.The results show that the photocatalytic CO2 reduction activity of CuTCPP/P25m composites is significantly higher than that of pure P25.The activity of 0.5%CuTCPP/P25m composites for methanogenesis can reach 19.39 ?mol/g/h.(2)CuTCPP[UiO-66/TiO2(CTU/TiO2)photocatalytic CO2 reduction:CTU/TiO2 composite catalyst was prepared by in-situ hydrothermal method,and photocatalytic reduction CO2 performance test was carried out.The possible photocatalytic reaction mechanism was proposed.The results show that the composite CTU/TiO2 has better photocatalytic activity than TiO2,and the rate of CO production by CTU/0.6TiO2 catalytic reduction can reach 31.32?mol/g/h.(3)PCN-222(Cu)/TiO2 photocatalytic CO2 reduction:rod-shaped metalloporphyrin MOF structure PCN-222(Cu),was prepared by controlling the ratio of benzoic acid to distilled water.This was combined with TiO2 to obtain a PCN-222(Cu)/TiO2 composite.A series of PCN-222(Cu)/TiO2 composites were tested for photocatalytic reduction of CO2.The results showed that 10%PCN-222(Cu)/TiO2 has the highest photocatalytic activity for its photocatalytic to CO2 reduction.The rate of formation was as follows:CO yield was 13.24 ?mol/g/h.