Design And Synthesis Of Two-Dimensional Conjugated Polymers For Appications In Photothermal Energy Conversion

Excessive consumption of traditional fossil energy not only faces the problem of energy exhaustion,but also causes severe pollution to the environment.The development of clean and renewable energy is imminent.Solar energy,as a new type of energy,has the advantages of abundant reserves,no pollution,no geographical restrictions,and no need for transportation.Therefore,efficient and simple conversion and use of solar energy has become an effective method to solve the energy crisis.Directly converting light energy into heat has higher energy conversion efficiency,and the heat energy obtained through solar energy conversion can be directly used for seawater desalination and household heating.At present,the materials used for photothermal conversion are mainly porous carbon,metal nanoparticles,and metal oxides.However,the high cost,as well as the complexity of the manufacturing process,structural and performance instability,limit the practical application of these materials.Therefore,developing low-cost,easy-to-process,and efficient and stable light-to-heat conversion materials still faces great challenges.On the other hand,two-dimensional materials have been widely used in electrical,optical,thermal,and mechanical fields due to their excellent physical and chemical properties.By adjusting the morphology and structure of the material and making it two-dimensional,it is expected to further improve its light-to-heat conversion efficiency and broaden its application in the field of light energy conversion.This doctoral thesis using two-dimensonal conjugated polymers as a platform,mainly focusing on preparing high-efficiency photothermal conversion materials through the regulation of its microstructure and macromorphology,and further in-depth studying the structure-effect relationship to provide new ideas for designing efficient energy conversion materials.The specific research content is summarized as follows:1.Two-dimensional polypyrrole nanosheets with ultra-thin layer morphology was obtained by using a spatially confined synthesis method,using layered iron oxychloride as a template,inserting a pyrrole monomer and performing in-situ oxidation polymerization.Due to its ultra-thin two-dimensional sheet structure,the prepared polypyrrole can adsorb a large number of ions during the acid hydrolysis of the template to achieve high doping,thereby causing bipolaron band to appear in the electronic structure of the polypyrrole nanosheet.This unique property makes the polypyrrole nanosheets exhibit extremely high optical absorption characteristics and light-to-heat conversion capabilities in the second near-infrared region,which greatly exceeds other previously reported inorganic/organic photothermal materials.At the same time,we also designed a series of cell experiments and animal experiments to further verify the efficient photothermal tumor elimination ability of ultra-thin two-dimensional polypyrrole nanosheets.This work has made important progress in the development of two-dimensional polymer materials for photothermal therapy,and also provides new ideas for the design and synthesis of more polymer nanostructures for the biological field in the future.2.Using the template method,multilayer polypyrrole nanosheets with surface microstructures were directly obtained on a variety of substrates by controlled layer-by-layer interface polymerization.Due to the difference in elastic modulus between the polypyrrole nanosheets and the carrier,when the polypyrrole nanosheets are grown on the substrate,the polypyrrole nanosheets will be deformed to release interfacial energy and form randomly distributed wrinkles on the surface.Thanks to the unique wrinkle structure of the multilayer polypyrrole generated during the polymerization process,incident light at different angles will be absorbed after multiple reflections on the surface of the polypyrrole,which promotes the omnidirectional light capture capability of the multilayer polypyrrole nanosheet.The light absorption rate of the obtained polypyrrole nanosheets in the solar spectral range exceeds 99%,the light-to-heat conversion efficiency under the irradiation of sunlight reaches 95.33%,surpassing other previously reported inorganic/organic photothermal energy materials.Due to the strong hydrogen bonding interaction between the polypyrrole and the substrate and the polypyrrole sheet layer and its own surface microstructure,the polypyrrole system has strong flexibility and bending resistance,which can withstand different degrees of mechanical deformation without affecting the photothermal conversion performance.It was futher applied to direct light-to-heat conversion,photo-actuated actuators,water vapor evaporation,etc.,all of which exhibit significant effects.This research provides new ideas and insights for designing simple and efficient light-to-heat energy conversion materials in the future.3.An ultra-thin conjugated microporous polymer with excellent light-to-heat conversion performance is used as a substrate,and its porous nitrogen-containing structure is used to adsorb metal ions to prepare an ionic metal catalyst.TEM,XRD,and XPS results showed that the obtained metal catalyst did not contain metal nanoparticles,and the metal was supported on the conjugated microporous polymer substrate in the form of ions.After applying the catalyst to the light-driven carbon dioxide carboxylation reaction,due to the photothermal properties of the conjugated microporous polymer near the ionic metal catalyst,the catalyst exposes significant light-driven catalytic performance in the catalytic carboxylation reaction without an external heat source,indicating its great potential in replacing thermally driven catalysis.The prepared metal catalyst also possesses excellent cycle stability and maintains a stable catalytic efficiency in multiple catalytic carboxylation reactions.This work provides new inspiration for the design and preparation of high-efficiency photothermal catalysts in the future.