The Preparation Of Novel Mof-based Nanocomposite And Its Application In Co₂ Photo-reduction

Due to population growth and sustained economic development,fossil energy has been consumed and utilized in large quantities,resulting in an increasing concentration of carbon dioxide in the atmosphere.The method of catalytic conversion of carbon di-oxide（CO₂）using visible light to chemical raw materials or fuels can reduce its con-centration,and at the same time manufacture chemical raw materials to benefit the sus-tainable development economy.At present,it is widely studied by scientists.Although scientists have continued research in this field for many years,the development of highly efficient photocatalysts and mechanism research are still in their infancy,largely due to the rapid recombination of photo-generated hole electron pairs and the low af-finity of the active site for CO₂ absorption.The metal-organic framework（MOF）material is a material composed of metal nodes and organic ligand connectors through a chemical force mainly composed of co-ordination bonds.Compounding MOF materials with different semiconductor materials to construct hybrid catalysts has become an effective method to enhance the photocata-lytic activity.However,these composite materials still have some shortcomings:（1）the composites usually own a photoinactive MOF component,which will shield light har-vesting;（2）the MOF nanosheets lack an explicit active center for direct strong interac-tion with accommodated QDs to create a directional path for effective charge transfer;（3）the decorated QDs are easy to aggregate or dissociate from the MOF nanosheets due to the weak interaction.In this thesis,the preparation of novel MOF photocatalyst is carried out for the above problems:1.A novel ultra-thin porphyrin MOF（PMOF）and g-C₃N₄ quantum dot（g-CNQD）hybrids was successfully prepared by self-assembly method for photocatalytic reduc-tion of CO₂.The 2D ultrathin nature of the PMOF and 0D g-CNQDs facilitates the direct coordinative interaction between g-CNQDs and the Co（II）center of porphyrin in PMOF,which leads to efficient separation of photogenerated charge carriers and effec-tive injection of excited electrons into Co（II）centers for CO₂ molecular reduction.Compared with bulk PMOF,the hybrid composite not only exhibits enhanced photo-catalytic CO₂ reduction activity,the CO generation rate is 16.10（?）mol g^-1 h^-1,the CH₄generation rate is 6.86（?）mol g^-1h^-1,and it also shows more preference for eight-electron reduced CH₄ production.The prepared 0D/2D hybrid composite has excellent charge transfer and effective light harvesting,and its composite strategy method is expected to be applied to the preparation of more photocatalysts.2.A novel catalyst composed of MOF and gold nanorods（Au NR）was prepared,which is designed to phororeduction carbon dioxide by the principle of surface plasmon enhancement（LSPR）.A series of porphyrin MOFs were prepared by wet chemical method,and gold nanorods with adjustable aspect ratio were synthesized by one-pot method.The composite materials of MOF and gold nanorods were prepared by self-assembly and in-situ synthesis.After using PVP for surfactant replacement,a thin layer of PCN-224 MOF was successfully wrapped on the surface of gold nanorods.The prep-aration conditions and synthesis methods of Au NR@PCN-224 core-shell structure were discussed,and certain optimization and material characterization were carried out.