Syntheses And Photo/Electro-Catalysis CO₂ Reduction Properties Of Metal-Organic Framework Based Composites/Derivatives Materials

Due to excessive exploitation and utilization fossil energy,dramatical increase of carbon dioxide（CO₂）concentration leads to the global greenhouse effect,which causes a series of serious environmental issues.Converting CO₂ into value-added chemicals via photocatalysis and electrocatalysis is an effective way to reduce CO₂ concentration.As the core component,the structure design and controllable synthesis of catalysts is the hot research field.Among various catalyst,due to their ultrahigh surface area,permanent porosity,structural diversity and designable framework topology,metal-organic frameworks（MOFs）composites/derived materials have unique advantages in photo/electro-catalytic of CO₂ reduction reaction.This thesis includes the following two main parts:（1）The"building-bottle-around-ship"strategy to prepare Cs Pb Br₃@ZIF-67 core-shell material:The as-prepared Cs Pb Br₃ quantum dots（QDs）via hot injection method were dispersed into ethyl acetate.The 2-methylimidazole and cobalt acetylacetonate were added into the mixed solution stepwise.The ZIF-67 shells gradually grew on the surface of Cs Pb Br₃ to obtain core-shell Cs Pb Br₃@ZIF-67.The Cs Pb Br₃@ZIF-67characterized by XRD,TEM and XPS tests.ZIF-67 as shell material improves the stability of Cs Pb Br₃ QDs,enhances the adsorption of CO₂ and promotes the separation of photogenerated carriers.In the case of water as sacrificial agent,the Cs Pb Br₃@ZIF-67 exhibits photocatalytic CO₂ reduction activity with CO yield of 24μmol g^-1 h^-1,3.16times of Cs Pb Br₃ QDs,and maintains high stability in catalysis.（2）The confinement strategy to synthesize single-atom metal implanted in N-doped carbon materials（Ni,Ni-N-C,Ni Ce-N-C and Ni La-N-C）:PCN-222 was filled with the mixture solution of metal complexes and urea,then dried by the vacuum freeze,and treated via thermal annealing and acid etching.TEM characterization showed that the rod-like structure of the parent PCN-222 was maintained and there were plentiful micropores on the surface.The electrochemical characterization shows that the rare earth metal La plays a better synergistic catalytic role than Ce element.Under the potential window of-0.9 to-1.1 V（vs.RHE）,the catalytic performance of Ni La-N-C is the best,with CO Faraday efficiency above 80%.The catalytic performance of Ni Ce-N-C was inferior,and.Electrochemical impedance measurement and Tafel slope show Ni La-N-C have lower mass transfer resistance and faster reaction kinetics,respectively,and thus Ni La-N-C has better catalytic activity.