Synthesis And Photocatalytic Application Of Heteroatom Containing Conjugated Porous Organic Polymers

Conjugated porous polymers are a class of fully conjugated polymers defined by high surface area and porosity in the nanometer range.On the one hand,diverse organic?-systems allow for flexible tuning of the visible light absorbance,so as to optimize charge transfer;On the other hand,porous systems can provide more active sites for photocatalytic redox reaction on the surface of catalysts.Therefore,conjugated porous polymers are actively pursued for promising applications in photocatalysis.So far,variety of works have been carried out for improving the photocatalytic activities of conjugated porous polymers,such as chemical doping,band gap tuning,surface modification,morphology controlling and so on.However,exploring the factors of photocatalytic performance by effective molecular designing is still challenged.Photocatalytic application of heteroatom adopted conjugated porous polymers in this thesis focuses on two parts:?1?Conjugated microporous polymers?CMPs?are a class of porous materials that permit the linking of building blocks in a?-conjugated fashion and possess three-dimensional networks.Since CMPs are synthetic polymers,various building blocks and linkages with versatile heteroatoms doping could be expected.However,some issues such as resident noble metals or transition meals in the process of synthesis as well as improving performance by morphology controlling still need to be resolved.In this part,a new series of CMPs were synthesized via designing different polyphenyl molecules in C₂,C₃,D_2hh symmetric monomers combined with polycondensation without addition of metal catalysts.First,the structure was determined by FT-IR spectra and solid-state NMR,and the porous structure and special layered nanosheets were characterized by nitrogen adsorption-desorption isotherm,atomic force microscope and scanning electron microscope.Superior photocatalytic activities of polymers were indicated by degrading organic dyes under visible light irradiation and different scavengers were added to explore the degradation mechanism.Finally,controlling experiments without chemical doping or layered structure were carried out to further exploring the factors of photocatalytic performance.?2?As another type of conjugated porous polymers,covalent triazine frameworks?CTFs?have special properties of rich nitrogen content and high chemical stability.CTFs have emerged as a very promising class of metal-free photocatalytic materials for solar water splitting.However,they generally exhibit low efficiency and lack the capability to utilize long-wavelength photons in a photocatalytic oxygen evolution reaction.In this part,CTFs with different porous structure and band gap position were prepared by introducing pyridine ring and tuning the shape of monomer molecules.Due to the different nitrogen content and monomer shape,light absorption and band gap position of CTFs were succeed to be tuned.Finally,the CTFs were loaded with metal Pt or Ru and applied to photocatalytic hydrogen and oxygen evolution reaction,respectively.The results showed that different energy band positions and light absorption properties of CTFs played important roles in photocatalytic water splitting performance.