Design,Synthesis And Photocatalytic Hydrogen Evolution Of Water/Alcohol Soluble Conjugated Polymers

Photocatalytic water-splitting technology,which is capable of producing clean,environmentally friendly and high-energy-density hydrogen fuel,provides an effective way to solve the energy crisis and environmental problems.In recent years,more and more organic conjugated polymer materials have been used in the field of photocatalytic hydrogen production due to their advantages of facile preparation,precise chemical structure,tunable opto-electronic properties etc.However,the photocatalytic performance for hydrogen evolution of most conjugated polymers is relatively low.It is challenging to design highly efficient and stable conjugated polymers-based photocatalysts.More efforts should be devoted to the investigation of the relation between chemical structures and photocatalytic performance of conjugated polymers-based photocatalysts.This dissertation aims to provide a deep understanding of the relation between chemical structures and photocatalytic performance of conjugated polymersbased photocatalysts.By designing a series of water/alcohol-soluble conjugated polymers with tailor-made building blocks and substituents in their main chains,the influence of conjugated polymer structure on the photocatalytic hydrogen production evolution is systematically studied.The main contents of this dissertation are described as follows:In chapter 2,we designed and synthesized three water/alcohol-soluble conjugated polymers with poly(fluorene-benzothiadiazole)backbones,which contains different substitutions(F atom,Cl atom and methoxy group).The effects of the substituents of the polymer on the hydrogen adsorption free energy,intramolecular dipole inside backbones,charge transfer to the cocatalyst as well as the photocatalytic performance for hydrogen evolution were systematically studied.The results show that the water/alcohol soluble conjugated polymer with fluorine and chlorine atoms as substitutions possess faster charge transfer efficiency from polymers to the cocatalyst,resulting in much better photocatalytic performance for hydrogen evolution than polymer with methoxy group as substitution.In chapter 3,we further broadened the absorption spectrum of water/alcohol soluble conjugated polymers in order to enhance the photocatalytic performance in visible light.Three water/alcohol soluble conjugated polymers with poly(benzodithiophene-benzothiadiazole)backbones were designed and synthesized.It was found that,compared to the polymer with the methoxy,the polymers with F atom,Cl atom as substituents showed much better photocatalytic performance for hydrogen evolution.In chapter 4,we designed two conjugated polymers(P7O-2N-2N and P7O-4N)with hydrophilic side chains and nitrogen-contained heterocycles in backbones.The chemical structures and their influence on the absorption spectrum,energy level,free energy of hydrogen adsorption and photocatalytic performance of the material were systematically studied.The study found that the conjugated polymer(P7O-4N)having a 3,6-bis(thien-2-yl)-1,2,4,5-tetrazine structure show stronger inter-chain aggregation,lower hydrogen bonding free energy,and better photocatalytic hydrogen production performance than polymers(P7O-2N-2N)with 2,5-bis(thiazole-2-yl)-pyrazide structure.