Synthesis Of Porphyrin-Based Conjugated Organic Polymers And The Application In Photocatalytic And Electrocatalytic Systems

Since the 18th century,mankind has achieved a major leap from manual labor to machine production.However,human beings’exploitation and utilization of global fossil energy is increasing with the development of science and technology,which causes many problems such as energy exhaustion and environmental degradation.Therefore,the development of renewable and clean energy has become the focus of people’s attention in the21st century.Solar energy and electric energy as the renewable clean energy have also come into people’s attention and derived a lot of research directions.Among them,photocatalytic hydrogen production and electrocatalytic carbon dioxide reduction are the current research hotspots.In this,three porphyrin-conjugated organic polymers（Zn-ZnDETPP,Co-CoDETPP and Zn-CoDETPP）containing different coordination metals were designed and synthesized in this paper,and they were applied to photocatalytic hydrogen generation system and electrocatalytic CO₂ reduction field.The main research contents are as follows:1.On the basis of the synthesis of metalloporphyrins,we designed and synthesized three porphyrin-conjugated polymers（Zn-ZnDETPP,Co-CoDETPP and Zn-CoDETPP）which containing different coordination metals.The porphyrin molecules were characterized by NMR,UV-Vis spectrum and MS.In addition,FT-IR,Raman spectroscopy,SEM,XRD,XPS and other methods were used to confirm the structure of target porphyrin-based polymer.The HOMO and LUMO levels of the three polymers were obtained by analyzing their UV-Vis DRS and UPS spectra.2.Porphyrin-based conjugated organic polymers（Zn-ZnDETPP,Co-CoDETPP and Zn-CoDETPP）were directly carried out to test their photocatalytic hydrogen production performance.The results show that Zn-CoDETPP exhibits the best hydrogen production activity of 43 mol h^-1（λ≥400 nm）compared to the other polymers.The results of steady-state fluorescence show that Zn-CoDETPP has higher carrier separation efficiency.Moreover,the results of theoretical calculation show that HOMO’and HOMO electrons of Zn-CoDETPP are mainly distributed on zinc porphyrin units,and LUMO’and LUMO electrons are mainly distributed on cobalt porphyrin units.In addition,the L-side absorption of Zn-CoDETPP proves that the valence state of cobalt changes from bivalent to monovalent during illumination.The above results show that Zn-CoDETPP can achieve electron transfer between the central metals in the light process,and thus effectively reducing its charge recombination and improving its carrier separation efficiency.3.In order to further develop the application of porphyrin-based conjugated organic polymer,Co-CoDETPP was selected for electrocatalytic CO₂ reduction.Whenη=490 mV,the Faraday efficiency of CO could reach up to 83%.In order to further improve its electrocatalytic performance,Co-CoDETPP/CNTs materials was synthesized and applied to the field of electrocatalytic CO₂ reduction.The morphology and structure of the composites were characterized by SEM,TEM,FT-IR and Raman spectroscopy.Under the same electrocatalytic test conditions,the electrocatalytic performance of Co-CoDETPP/CNTs composite is significantly higher than that of Co-CoDETPP and the Faraday efficiency of CO can reach up to 91%（η=490 mV）.