Preparation And Properties Of Phthalocyanine-Based Conjugated Organic Framework Electrocatalytic Materials

With the accelerated consumption of traditional fossil energy,the energy crisis and environmental pollution problems caused worldwide are gradually increasing.In view of this,it is urgent to develop large-scale clean and efficient energy storage and energy conversion technologies.Using them to meet the demand of renewable energy production and load,and promote the transformation of the existing energy structure is one of the important measures to achieve the dual carbon goal,such as fuel cells,metal air cells and other energy conversion devices.These devices effectively achieve the mutual conversion between chemical and electrical energy and the core component of which is electrochemical reactions,mainly including oxygen reduction reaction（ORR）,oxygen precipitation reaction（OER）,etc.Therefore,improving and developing electrocatalysts with excellent electrocatalytic performance is the core and key to realize the efficient operation of these new energy converter devices.Currently,the electrochemical reaction is dominated by precious metal based electrocatalysts represented by Pt,Ir,Ru,etc.,which show excellent catalytic activity in the catalytic process and are highly relied on in practical applications.However,the natural storage of precious metals is limited,and the scarcity of resources has led to an increase in the cost of precious metal based electrocatalysts,which has greatly limited the commercial application of such catalysts.At the same time,due to the instability of precious metal-based eletrocatalysts,metals tend to gather and form nanoparticles when operating in harsh environments for a long time,which greatly affects the activity of electrocatalysts and the reaction efficiency of energy devices.Therefore,utilizing new materials to develop non precious metal materials with high ORR/OER catalytic activity,easy processing,and fast electron transfer is the key to breaking through the large-scale application of clean energy technologies.Two-dimensional conjugated organic framework materials have attracted wide interest in the field of electrocatalysis due to the easy directional regulation of components,abundant active sites and excellent structural stability.The structure-activity relationship in electrocatalytic materials can be deeply understand by adjusting the coordination environment of the materials.The materials can not only regulate and improve the catalytic activity,but also provide a strong support for in-depth understanding the structures-activity relationship of electrocatalysts.However,problems such as poor intrinsic conductivity and difficult exposure of active sites caused by interlayer accumulation restrict the electrocatalytic activity of such materials and breakthroughs in practical application scenarios.Therefore,improving the intrinsic conductivity of two-dimensional conjugated organic framework materials,improving the electron/charge transfer rate and reducing the number of two-dimensional lamellar structures can effectively improve the mass transfer efficiency of electrocatalysts and increase the effective electrocatalytic activity density,so as to effectively improve the electrocatalytic activity of two-dimensional conjugated organic framework materials.Based on the above background,this paper takes"phthalocyanine-based conjugated organic framework material"as the research foundation.Aiming at energy electrocatalysis,this paper builds phthalocyanine-based conjugated organic framework electrocatalyst with clear structure by means of pyrolysis-free strategy,systematically studies the relationship between material structure and catalytic activity of ORR/OER,and explores the relationship between the type of metal center,catalytic activity and catalytic type.Exploring the relationship between solubility and the interaction force between material structure in response to the difficulties in processability of this type of electrocatalyst in practical applications,which affects the full utilization of catalytic performance.Meanwhile,in view of the electron transfer problem of this kind of catalytic materials,the intrinsic conductivity of highly ordered phthalocyanine network structural materials is explored by constructing a closed conjugate system.The main research contents are as follows:（1）Design and construction of conductive two-dimensional conjugated organic frame materials.The tailorability and diversity of organic framework materials can precisely extend individual organic molecules to well-defined framework materials,providing a good platform for the design of material properties.By combining organic framework materials with conductivity,it is expected to simultaneously meet the basic requirements of electron（charge）transfer and high catalytic performance in frame-type electrocatalytic materials.However,only a few organic framework materials with limited p-type charge mobility have been reported,while the development of n-type conductive organic framework materials is still lacking.With the help of phthalocyanine groups,this paper develops an n-type conductive organic framework material composed of a two-dimensional（2D）conjugated structure of nitrogen coordinated cobalt atoms.High electron delocalization degree is achieved by constructing fullπ-conjugated structure,which enhances the free transport of electrons along the plane direction,and improves the stability of the plane structure under acidic/alkaline conditions.The prepared COF_BTC-CO possesses metal-like conductivity characteristics and n-type conductivity behavior,with a charge mobility of 9.39 cm ²V^-1S^-1at 300 K and a conductivity of 0.14 S cm^-1at-5 V bias.It exhibits excellent potential in the field of electrochemical catalysis.This work provides a new solution for improving the electrical conductivity of mesh frames and broadening their applications in the field of electrical conductivity.（2）The structure and van der Waals interaction modulation of solution processable conjugated organic framework materials.Organic framework materials have been widely developed in fields such as catalysis,energy storage,and conversion due to their excellent controllability,stability,and porosity.However,their non processable powder properties limit their development.In this paper,organic framework materials have been widely developed in fields such as catalysis,energy storage,and conversion due to their excellent controllability,stability,and porosity.However,their non processable powder properties limit their development.The newly developed COF_NTC-Fe achieves the expansion and extension of the conjugated structure by extending the number of benzene rings in the reaction monomer.Compared with COF_BTC-Fe,it exhibits smaller interlayer interactions,enabling the material to achieve a faster dissolution process in the same solution.Experiments and molecular dynamics simulations show that COF_NTC-Fe is more prone stripped and dissolved in the same solvent due to smaller interlamellar van der Waals forces.On this basis,the organic transport layer of perovskite quantum dot light-emitting diode（perovskite LED）was prepared by liquid processable method using the properties of materials.This work provides a new method for the preparation of soluble COF materials,achieving a breakthrough in the processing performance of conjugated organic framework materials,and providing a strong guarantee for the device assembly and application field based on this kind of materials.（3）Metal centers and electrochemical performance regulation of phthalocyanine based conjugated organic framework materials.In this paper,the corresponding phthalocyanine-based conjugated organic framework material COF_BTC-M（M=Fe,Co,Ni,Mn,Cu,Zn）was obtained by controlling the type of precursor metal salts and controlling the type of metal in the active center during the synthesis process.Through three electrode testing,the influence of different metal centers on the catalytic performance of this type of phthalocyanine based conjugated organic framework material in the electrochemical oxygen reduction process was explored.When the metal center was Fe,the phthalocyanine-based conjugated organic framework material showed excellent electrocatalytic activity of oxygen reduction.The half-wave potential of COF_BTC-Fe electrocatalyst could reach 922 m V in 0.1M KOH,and the reaction was dominated by four-electron reaction path.At the same time,the catalyst showed the smallest Tafel slope and the highest reaction kinetic transfer coefficient and deeply revealed the impact of metal center changes on the oxygen reduction electrocatalytic activity of metal phthalocyanine based conjugated organic framework materials.On this basis,in this paper,commercial carbon felt is used as flexible fluid collecting material,and COF_BTC-Mn,which is the most abundant metal valence state,is used as the active material for flexible electrode of supercapacitor.Through electrostatic adsorption,laminate COF_BTC-Mn material is uniformly adsorbed on the surface of carbon fiber to construct flexible electrode directly used for supercapacitor.Furthermore,the influence of changes in the metal center of the material on the charging and discharging process is further expanded and studied,and lays a theoretical foundation for the application of this type of phthalocyanine based conjugated organic framework material in the field of electrochemistry.（4）Research on the construction of bifunctional oxygen electrocatalysts using pyrolysis-free strategy and their structure-activity relationship.Transition metal nitrogen carbon（M-N-C）catalysts with MN₄active centers have received widespread attention as potential substitutes for precious metal catalysts in bifunctional and even multifunctional electrochemical catalysis.However,the charge environment of MN₄active site obtained by conventional pyrolysis strategy is asymmetric,which makes the adsorption of oxygen molecule unbalanced,and restricts the activity of oxygen evolution reaction（OER）and oxygen reduction reaction（ORR）.In this paper,a series of quasi phthalocyanine conjugated two-dimensional（2D）covalent organic polymers(COF_BTC-M)with MN₄₊₄active site was developed through pyrolysis free strategy.Compared with the MN₄site constructed by traditional pyrolysis,the additional nitrogen atoms on the MN₄₊₄site balance the charge environment,form a symmetrical charge distribution,change the antibonding molecular orbital of the active metal in the structure center,adjust the adsorption of oxygen molecules,thus improving the bifunctional oxygen electrocatalytic activity.Through screening of different metal centers,it was found that the cobalt pair COF_BTC-Co with MN₄₊₄site showed the best ORR and OER activities for oxygen adsorption and desorption in the best equilibrium state due to the fewer antibonding molecular orbital below the Fermi level.Both theoretical and experimental results confirm that the COF_BTC-Co catalyst has a unique Co N₄₊₄active site and optimal catalytic activity,with a potential difference of 0.76 V,and also exhibits excellent kinetic performance.The zinc-air flow battery directly assembled from it exhibits excellent discharge power density(157.7 m W cm^-2)and excellent stability.This work not only provides an understanding of the inherent active species of MNx centers,but also provides a new approach for designing advanced bifunctional electrocatalysts.