Preparation And Investigation On Photocatalytic Performances Of Organic Polymer Based Semiconductor Materials

The energy crisis and environmental deteriorition have become two major problems restricting the sustainable development of human society,which need to be solved urgently.Photocatalytic technology based on semiconductors has displayed great potential in treating energy and environmental issues.However,traditional inorganic semiconductors have the disadvantages of narrow light absorption range,low separation efficiency of charge carriers and trouble in tuning the band structure.The utilization of photons and the photoconversion efficiency are unsatified.Therefore,developing of novel and efficient photocatalysts has become one of the research topics in this field.Herein,based on the facile tuning of structure for polymers,three types of conjugated organic microporous polymers and one organic/inorganic hybrid were prepared.Their photoelectrochemical properties and photoreduction performance towards CO₂ were investigated.These researches provide some new ideas and strategies for developing of highly efficient photocatalysts.The specific research contents of this paper are as follows.1.Three conjugated microporous polymers（CMPs）based on thiophene,furan and carbazole funional groups were synthesized via the Sonogashira-Hagihara coupling method.The composition and structure of these CMPs were characterized by FT-IR and ¹³C MAS-NMR,which confirmed the successful preparation of these samples.The band structures of CMPs were determined by UV-vis DRS and UPS,the bandgap for thiophene,furan and carbazole CPMs are 2.11 e V,1.95 e V and 1.81 e V respectively.SEM images displayed that CMPs are regular nanospheres,and the diameter of them is ranged from 1-3μm.The photocatalytic CO₂reduction based on the CMPs is conducted without any cocatalyst and sacrificial agent.Among them,thiophene based CMP showed the highest photocatalytic activity.The yield for CO reached 1178.4μmol·g^-1upon irradition for 6 h,which was 2.1 times and 2.5 times of the carbazole and furan based CMPs,respectively.The thiophene unit in the CMP can effectively activate the CO₂ adsorbed on the catalyst,which reduces the activation energy of photoreduction.2.g-C（CN）₃ was synthesized by polymerization of ionic liquid based on iminazole.Subsequently,the Z-Scheme heterojunction（Bi VO₄/g-C（CN）₃）was prepared through in-situ loading of g-C（CN）₃on the surface of Bi VO₄.The composition and structure of Bi VO₄/g-C（CN）₃ were characterized by XRD,Raman,FT-IR,XPS,SEM and TEM.Bi VO₄/g-C（CN）₃displayed a erythrocyte-like hollow structure.The photocatalytic CO₂ reduction based on Bi VO₄/g-C（CN）₃ is conducted without any cocatalyst and sacrificial agent,the optimized Bi VO₄/g-C（CN）₃-20 showed the highest photocatalytic activity.The yield for CO reached244.8μmol·g^-1 upon irradition for 6 h,which was 156 times and 7 times of the bare Bi VO₄and g-C（CN）₃,respectively.The interface between Bi VO₄ and g-C（CN）₃effectively promotes the separation efficiency of photogenerated electron-hole pairs.In combination of superior accumulation and activation capacities of g-C（CN）₃,the photocatalytic performance of the Z-Scheme Bi VO₄/g-C（CN）₃was significantly improved.