Biomimetic Design Of Artificial Photosynthesis System Based On Photo-Enzymatic Coupling Model

Construction of artificial photosynthesis system by incorporating the solar energy driven photochemical regeneration of coeznyem NADH with the redox enzymatic process to produce various fuels or chemicals has an important significance for solving energy and environmental crisis.However,how to create a direct photocatalytic and enzymatic interface to facilitate the transfer of the photo-excited electrons in photosensitizer,electronic mediator,cofactor and oxidoreductase still remains a big challenge.Inspired by the structure and mechanism of natural photosynthesis system,this thesis was aimed at biomimetic design of artificial photosynthesis system based on photo-enzymatic coupling model for conversion methanol from CO2.This thesis mainly includes the following three aspects:firstly,hybrid hollow nanofibers were prepared and used as a scaffold for accurately assembling elements of artificial photosynthesis.The transfer efficiency of excited electrons could be improved by shortening the distance of the electron transfer chain.Secondly,based on the predominant optoelectronic and assembly load capacity,we constructed two-dimensional TaS₂ nanosheets-based electrons transfer chain with enhanced efficiency.Thirdly,we constructed efficient electrons excitation and transfer system based on single molecular by bottom-up chemical synthesis method.The specific research contents include the following:?1?Preparation,characterization and application of polyelectrolyte doped hollow nanofibers:polyelectrolyte?PAH?doped hollow nanoflbers with positively charged ionogen groups distributing on their inner and outer surface were prepared by combination of coaxial electrospinning technology and self-assembly technology.The retention and reuse of cofactors,and positional assembly multienzyme system for conversion methanol from CO2 on nanofibers surface or in their hollow chambers were realized based on the ion-exchange interactions between oppositely charged enzymes/NAD?H?and PAH that was doped in hollow nanofibers.And the yield of methanol reached to 103.2%.Besides,the polyelectrolyte doped hollow nanofibers membrane was found to float spontaneously at the O/W interface,thus providing opportunity to develop novel interfacial active biocatalyst.When an hollow nanofibers-based interfacial cascade bienzyme systems lincluding glucose oxidase?GOD?and CALB lipse were prepared and used for epoxy stearate synthesis in an oil-aqueous biphasic system,the highest reaction rate was attained by lumen?GOD?-surface?CALB?,corresponding to 114.45 times enhancement as compared to that of the free bienzyme system.?2?Integrated artificial photosynthesis based on polyelectrolyte-doped hollow nanofibers:inspired by the structure of green plant chloroplasts,the biocatalysis part including multiple oxidoreductases and coenzymes NAD?H?was in situ encapsulated inside the lumen GO and PAH doped hollow nanofibers fabricated via co-axial electrospinning;while the precise and spatial arrangement of the photocatalysis part,including electron mediator and photosensitizer for photo-regeneration of the coenzyme,was achieved by ion-exchange and ?-? interaction-driven LbL self-assembly.The highly integrated artificial photosynthesis with GO mediated electron transfer was realized.Compared to solution-based systems,the methanol yield increased 10 times using the integrated artificial photosynthesis.?3?Artificial photosynthesis based on TaS₂ nanosheets:the integration of M to TaS₂ nanosheets was realized through sequential functionalization by probe sonication,pegylation with lipoic acid conjugated PEG?LA-PEG?,surface assembly of graphene?GR?,and final integration of M.Two-dimensional TaS₂ nanosheets with assembling M,made electrons transfer in two dimensional scale with enhanced efficiency.The integrated photocatalyst termed as TaS₂-PEG-GR-M exhibited significantly improved efficiency with a NADH regeneration yield up to 83.9%and the formic acid converted from CO2 reached 101.4 mM in 5 hours.?4?Chloroplast mimicking artificial photosynthesis:the TCPP/SiO2/Rh HNPs are fabricated via sol-gel reaction of silica precursors functionalized with photosensitizer?porphyrin,TCPP?and electron mediator?Cp*Rh?bpy?Cl,M?;while the integrating of enzyme and NAD?H?on the outer surface of the HNPs were achieved through electrostatic interactions driven assembling under the entanglement of a negatively charged polyelectrolyte.The chloroplast-mimicking,highly integrated APS exhibits remarkably superior performance over free system,such that the regeneration of NADH is improved from 11%to 75%,and the synthesis of formic acid from CO2 increased from 15 mM to 100 mM in 4 hours.?5?Chlorosome mimicking artificial photosynthesis:TCPP/EYx/Rhg8-x macromolecules,synthesized through sequential amidation reaction between TCPP,EY,and[Cp*RhCl2]2,was found to self-assembled into chlorosome-mimicking supramolecular assemblies through ?-? stacking,hydrogen bonding and ion-exchange interactions.TCPP/EYx/Rh8-x supramolecular assembly not only realized photosensitizer sensitized and electron transfer chain construction on single molecular scale,but also evolved intramolecular electron transfer to intramolecular electron,which was expected to fundamentally solve the low electron transfer efficiency of artificial photosynthesis.The yield of NADH photo-regeneration using TCPP/EYx/Rh8-x supramolecular assembly was improved 91%,and the conversion of methanol from C02 increased to 38?M coupling with biocatalyzed system in 2 hours.