Synthesis And Properties Of Porous Aromatic Frameworks Prepared Via Suzuki-Miyaura Coupling Reaction

In recent years,porous aromatic frameworks?PAFs?have been widely praised by material scientists and chemical scientists as new porous organic materials.There is a high density of rigid aromatic rings in the PAFs backbone,and the aromatic structural units are completely connected by stable carbon-carbon single bonds.The uniqueness of the above structure makes PAFs have many excellent properties,such as strong structure,large surface area,high thermal stability and high chemical stability.Since the pioneering work of PAF-1 developed by our group,a variety of PAFs have been synthesized by scientists around the world and widely used in separation,adsorption,sensing,and heterogeneous catalysis.In the first part of this thesis,four new PAFs?PAF-111,PAF-112A,PAF-112B and PAF-113?have been synthesized by the polymerization of a tetrahedral-shaped?four-node?monomer with a series of three-node monomers through Suzuki–Miyaura coupling reactions.All the obtained PAFs possess hierarchical porous structures and show high thermal and chemical stability.The BET surface areas of PAF-111,PAF-112A,PAF-112B and PAF-113 were 857 m²/g,526 m²/g,725 m²/g and 598m²/g,respectively.Then,Rhodamine B?RB?was selected as the model organic dye to test the adsorption capacity of the obtained PAFs for organic dyes.PAF-111 showed a maximum adsorption capacity of 1666 mg/g?167 wt%?for RB,which is among the highest values reported to date for porous organic materials,The maximum adsorption capacities of PAF-112A,PAF-112B and PAF-113 for RB were 667,909 and 588mg/g,respectively.It is noteworthy that PAF-111 could be reused in at least ten cycles under the adsorption conditions without any loss adsorption capacity.Our study has revealed the great potential and advantages of PAFs as ultrastable adsorption materials for the removal of organic dyes.In addition,the four PAFs also exhibited good gas adsorption properties.At 273 K,1.0 bar,the CO₂ uptake capacities for PAF-111,PAF-112A,PAF-112B and PAF-113 are 2.22 mmol/g,1.36 mmol/g,1.49 mmol/g and1.60 mmol/g,respectively.In the second part of this thesis,we selected PAF-111 with high BET surface area as the platform.The basic ionic liquid sites were introduced into PAF-111through a series of post-modification methods,affording a basic heterogeneous catalyst PAF-111-IL?OH?.Benzaldehyde and malononitrile were selected as model substrates for screening reaction conditions,and the catalytic properties of PAF-111-IL?OH?for the Knoevenagel condensation reaction under different conditions were studied.After screening,we obtained the optimized conditions,and under the optimized conditions a series of benzaldehyde derivatives and cyclohexanone all could give a high reaction yield.PAF-111-IL?OH?has good stability as a catalyst and can be easily separated from the reaction mixture and can be reused to catalyze the reaction.The experimental results show that there is almost no loss of catalytic activity for PAF-111-IL?OH?after 10 cycles of the catalytic reaction.This part of the work demonstrates the attractive prospects of PAFs in the immobilization of ionic liquids.