The Design Of Biomimetic Catalysts And Its Application In Organic Transformation

In Nature,enzymes are the most efficient catalysts,which play an irreplaceable role in metabolism,photosynthesis and biological nitrogen fixation.As enzymes can specifically and efficiently catalyze various reactions in mild condition,great success have been obtained by applying them to organic synthesis as well as the new drug discovery.However,enzymes usually possesses poor stability as well as high cost,while they are easy to be inactive,so it is of research and application value to develop artificial enzyme system.Based on the research on homogeneous and heterogeneous biomimetic catalysts,using single-atom catalysts（SAC）which combine the merits of both homogeneous and heterogeneous catalysts to imitate active sites in metallozymes currently received wild attention from the scientific and the industrial.Baesd on above advantanges,catalysts loaded with Mn and Pt single atoms were synthesized by mimicing the natural metalloenzymes and evaluated their performance in phtocatalytic oxidation of N-heterocyclic compounds as well as the regeneration of NADH cofactor.The main contents are as follows:1.The synthesis of biomimetic Mn SAC and its catalysis applicationMimicking the synergistic mechanism between active sites and the second shell in metallozymes,a metal activation/substrate adsorption biomimetic synergistic catalysis system was prepared.The graphite carbon nitride photocatalyst with atomic Mn sites（Mn₁/C₃N₄）was prepared through the polymerization-impregnation-activation method.This biomimetic catalyst exhibited excellent catalytic activity,chemical stability and substrate compatibility in photocatalytic oxidation of N-heterocylic compounds.The theoretical calculation and experimental analysis revealed that the Mn-N₂ sites activate O₂to·O₂^-while the tri-s-triazine units adsorped the substrate throughπ-πstacking interaction.The interaction between single atoms and substrate stimulates the synergistic effects of active sites and the second shell in metalloenzymes.In this part,the active sites and its local environment in biomimetic catalysts was rationally constructed,after which evaluating its potential in fine chemical synthesis.2.The synthesis of biomimetic Pt SAC and its catalysis applicationInspired by the reversible catalysis of hydrogenase enzymes,a biomimetic metal/substrate catalysis system was constructed to catalyze the oxidation and reduction of cofactors.Through photodeposition process,Pt atoms was anchor on the surface of photo-responsive Ti O₂ substrate.XRD,TEM and STEM characterization were applied to prove that there is no metal nanoparticles or clusters in this catalyst.All the Pt species are atomically dispersed on the substrate.In NADH regeneration process,Pt₁/Ti O₂ is able to drive the reduction of NAD⁺with using hydrogen as reductant.Then a series of control experiments were conducted to explore the best synthesis method and reaction conditions.On the other hand,as the Ti O₂ sbstrate own photo-responsive ability,Pt₁/Ti O₂ sample can reversely catalyze the oxidation of NADH to NAD+in inert atomsphere with illumination.Experiments confirmed that Pt atoms accelerat the reaction kinetic process.In this part,Pt SAC was synthesised and suggested its potential in NADH oxidation/reduction cycle.