A Novel Porous Polymer Based On Thiophene And Its Photocatalytic Hydrogen Production

Due to the continuous consumption and use of fossil energy such as oil and coal,the exhaust gas such as carbon dioxide is discharged into the atmosphere,causing environmental problems such as greenhouse effect.It is of great importance to find alternative clean and environmentally friendly new energy.Hydrogen energy is an ideal clean energy because of its advantages of high combustion value,non-toxic and pollution,high utilization rate and convenient transportation.Sunlight is an inexhaustible resource,so hydrogen evolution through solar energy hydrolysis reaction is more in line with the concept of green environmental protection.Photolysis water material system can be divided into inorganic semiconductor photocatalyst and organic semiconductor photocatalyst.Inorganic semiconductors can be divided into excessive metal oxides,sulfur oxides,etc.Organic semiconductor can be divided into carbon nitride photocatalyst and organic conjugated photocatalyst.Compared with traditional inorganic semiconductors,organic conjugated polymer photocatalysts have the advantages of clear structure,adjustable photoelectric properties and high visible light efficiency,so they are regarded as the most promising materials for photocatalytic hydrogen production.The activity of photocatalyst is influenced by many factors,the specific performance in the migration rate of specific surface area carrier Visible light absorbing capacity and light hole-electronic on separation efficiency and the recombination rate.In this paper,by constructing a series of porous polymer conjugate,can control material very band gap specific surface area and the absorption of visible light and other factors,which affect the photocatalytic activity.The main factors affecting the photocatalytic hydrogen production performance of organic conjugated porous polymers were systematically studied.The specific experimental scheme and research direction were as follows:（1）Effect of fluorine atom on the photocatalytic hydrogen production performance of organic porous conjugated polymers:Three kinds of polymers with different number of fluorine atom TB-CPP,TBf2-CPP and TBf4-CPP were designed and synthesized,and the effect of fluorine atom substitution on the photocatalytic hydrogen production performance of polymer was systematically studied.The experimental results show that the introduction of fluorine atom with strong electron-absorbing ability leads to the red shift of the material,increases the specific surface area of the material,expands the absorption range of sunlight,and has more active sites,improving the performance of photocatalytic hydrogen production.These results suggest that the introduction of fluorine atoms into the polymer framework may be an effective strategy to improve the performance of photocatalysts.（2）Effect of conjugation length on photocatalytic hydrogen production performance of organic porous polymer materials:T-Tf4 and TT-Tf4 were synthesized by copolymerization of bis thiophene tetrafluorobenzene with thiophene and benzothiophene of different conjugated lengths.The physicochemical properties,carrier migration efficiency and photocatalytic activity of the materials were analyzed.The effect of conjugate length on the photocatalytic performance of conjugated porous polymers was investigated.The results show that TT-Tf4 copolymerized with benzothiophene has higher specific surface area,larger light absorption range and smaller charge transfer resistance.Therefore,the hydrogen production rate of TT-Tf4 at the full spectrum of 986μmol·g^-1h^-1is eight times that of T-Tf4.The difference of photocatalytic hydrogen production may be due to the increase of conjugation degree.（3）BTT was used as the main copolymer unit and copolymerized with 2FB and 2FBT structures to synthesize 2FB-BTT and 2FBT-BTT and to study their performance in photocatalytic decomposition of water for hydrogen production.The effect of introducing thiophene Joe bonds on the polymer backbone on the photocatalytic activity was investigated.The results showed that the hydrogen production rates of the two polymers reached 1462.1μmol·g^-1h^-1and 2135.8μmol·g^-1h^-1in the full spectrum,respectively,demonstrating excellent photocatalytic performance.When compared with 2FB-BTT,2FBT-BTT with the introduction of thiophene Joe bond has more red-shifted UV absorption,better optical properties and electrochemical properties.These show that the introduction of thiophene Joe bonds can produce a certain degree of improvement in the photocatalytic performance of the conjugated polymers,and demonstrate that the thiophene-containing polycyclic aromatic unit BTT is an excellent photocatalyst donor unit.