Design,Synthesis And Functionality Study Of Pillararenes And Porpyhrin Based Supramolecular Optoelectrical Materials

In the 21st century,with the fast development of society,our demand for energy has been increasing along with the continuous improvement of living standards.At the same time,the practical impact of the environmental problems to our lives has become increasingly prominent.The development of new types of materials to increase the energy utilization efficiency,reduce and capture polluting gases,and the utilization of renewable energy have become the most popular and challenging fields in materials science.Conjugated materials,which were firstly developed at the end of last century,are considered to be the best choice for solving energy and environmental problems in the new era attribute to their highly adjustable optoelectrical properties.And they are currently widely studied by scientists from materials,chemistry and physics backgrounds.Supramolecular chemistry is a new chemical method for building large molecular structures that goes beyond traditional chemical bonds.The use of such methods to prepare novel functional materials can often achieve characteristics that traditional covalent bond synthetic materials do not possess,such as constructing multicomponent supramolecular polymers through simple process,selective recognition of small molecules,etc.Here,we focus on the design and synthesis of functional organic conjugated systems.By using supramolecular chemistry as a material system construction strategy,we successfully prepared a series of conjugated material systems for organic light-emitting diode fabrication,carbon dioxide adsorption,and photocatalytic hydrogen production.In chapter 2,we designed and synthesized fluorescence supramolecular polymers based on pillar[5]arenes.Unlike conventional conjugated polymers,supramolecular polymers combine the advantages of solution processability and are assembled from small molecules.There are no batch to batch problems and no metal residual for the obtained supramolecular polymers.We successfully prepared blue-emission supramolecular polymer SP1 and green-emission supramolecular polymer SP2 and SP3 formed by interaction between pillar[5]arenes host and alkylimidazole guest.All three polymers exhibited similar photophysical properties to their analogous traditional conjugated polymers and showed a fluorescence quantum yield of up to 81.6%.All of these supramolecular polymers have been successfully used in the fabrication of organic light-emitting diodes,and the maximum device efficiency is close to 5cd A^-1.In chapter 3,we continued to take advantage of pillararenes which show high binding constants for neutral small molecules.We designed novel conjugated microporous polymer structures with highly selective adsorption for carbon dioxide by incorporating pillar[5]arene ring in the backbone of the polymers.After a series of synthetic attempts,we overcame the obstacle of large steric hindrance of the pillar[5]arene for polymerization,and finally obtained two conjugated microporous polymer materials ThrAP5 and PorAP5 that with complete pore structure.The specific surface area of ThrAP5 reached 2.2 cm³ g^-1,and the carbon dioxide adsorption capacity was 4.3 mmol g^-1.With the further increase of the length of the copolymerization unit,the specific surface area of the polymer PorAP5,which was copolymerized with porphyrin unit,is further increased to 5.6 cm³ g^-1,and the carbon dioxide adsorption capacity reached 6.9 mmol g^-1.Compared to similar porous material,the intervention of pillar[5]arene units significantly enhances the selective adsorption of carbon dioxide.In the fourth chapter,we designed and synthesized three hydrophilic conjugated small molecular PF2H,PFZn and PFCu for photocatalytic hydrogen production from water.The three small molecules are similar in chemical structure and have hydrophilic side chains.Experimental results showed that such structure is favorable for its dispersibility in water,and a highly uniform and efficient photocatalytic system can be obtained easily.The main difference is the type of the porphyrin center metal.The PF2H and PFZn centers are relatively electron deficient,while the PFCu center is an electron-rich environment.Through photocatalytic hydrogen production,PFZn molecules exhibited the highest photocatalytic activity,and their hydrogen production efficiency reached 1.1 mmol h^-1 g^-1,while only a small amount of hydrogen can be produced using PFCu as photocatalyst under the same conditions with an efficiency of 0.2 mmol h^-1 g^-1.In the last chapter,we designed and synthesized a water-soluble conjugated small molecule PFZnBr,and innovatively took advantage of the chloride ions in seawater to induce the formation of PFZnBr superstructures by electrostatic interaction to improve its photocatalytic efficiency.Our research demonstrated that PFZnBr showed a low hydrogen production rate of0.2 mmol h^-1 g^-1 under monodisperse conditions due to the limited intramolecular charge transfer efficiency.However,the supramolecular superstructures in seawater provided a platform for loading co-catalyst and promoted intermolecular charge transfer.As a result,the photocatalytic hydrogen production efficiency reached 10.8 mmol h^-1 g^-1.This is also one of the highest efficiencies reported using organic semiconductors for photocatalytic hydrogen production.We have further studied the photogenerated charge carrier transport rate before and after the formation of the assembled structures and found that the particle size of the particles plays a key role in the charge carrier transfer dynamic.