Preparation Of Bimetallic Porphyrin-based Covalent Organic Framework Materials And Study Of Their Electrocatalytic Carbon Dioxide Reduction Performanc

In the context of"carbon neutrality",electrocatalytic carbon dioxide reduction（CO₂RR）technology has attracted much attention due to its advantages of efficient carbon capture and low energy consumption.To explore a variety of highly efficient electrocatalysts to improve the catalytic activity and selectivity of CO₂RR is the key to the practical application of the technology.Covalent organic framework materials（COFs）have the characteristics of physical and chemical properties can be adjusted on the molecular scale,which is an ideal platform for bridging molecular catalysts and heterogeneous catalysts,and have good application potential in CO₂RR.Embedding metal porphyrins with CO₂RR activity into the COFs framework can improve their solubility and conductivity properties.However,because the extendedπdomain structure of COF changes the electronic structure of the metal atomic center,the CO₂RR performance of the obtained COF is lower than that of the corresponding metal porphyrins molecular catalysts.In this paper,porphyrinyl COF（COF-366-CO and COF-367-CO）was used as the research object to explore the structure-activity structure-activity relationship of catalysts.By changing the distance between Co atoms and constructing bimetallic COF atoms,the intrinsic activity of catalytic sites was improved.The specific research contents are as follows:（1）Based on Alder reaction,5,10,15,20-tetrad（4-aminophenyl）porphyrin was prepared with p-nitrobenzaldehyde,pyrrole and nitrobenzene as substrates,and the reaction time,temperature and post-treatment method were optimized.It is then combined with Co to form aminoporphyrin Co and then combined with intermediates to form COF.In order to explore the structure-activity structure-activity relationship,amino porphyrin and amino porphyrin Co were further used to form amino porphyrin-amino porphyrin co-COF through the linkers.It was found that the activity of catalyst increased with the addition of amino porphyrin.The Faraday efficiency of COF without amino porphyrin was improved by about 10%.Combined with XPS analysis,Co²⁺increased significantly after incorporation of amino porphyrins,while the amount of unincorporated COF was relatively small.Therefore,the higher the distance between Co atoms,the better the performance of CO₂RR electrocatalyzed by Co²⁺atoms in the catalyst.（2）Ni,Cu and Zn containing d orbital electrons and Mg without d orbital electrons were introduced into COF respectively to construct a bimetallic platform to increase the catalytic activity.The results show that the best performance of the combination than cobalt copper and cobalt magnesium metal combination.The amino porphyrin COF of cobalt copper can increase the performance to 99%,while maintaining good stability within 12 hours.Cobalt-magnesium amino porphyrin COF can increase Faraday efficiency to more than 90%at multiple voltages.