Synthesis And Adsorption Properties Of Porous Organic Polymers Based On Pillar[5]arene

Porous organic polymers?POPs?,emerge as a new kind of porous materials constructed by organic building blocks,with many advantages of designable building blocks,high thermal stability and chemical stability,large surface areas and tunable pore sizes,exhibiting enormous potential applications in many fields,such as gases adsorption and separation,catalysis,energy storage,drug delivery systems,etc.Introducing macrocycles as the key component into POPs represents a new type of porous materials,in which the cavity of macrocycles together with pores formed during the formation of polymers make up the multilevel pore structure,and contributes to increasing the specific surface area and expanding the application fields.Pillar[n]arenes as a new generation macrocyclic compounds,possess symmetrical pillar-shaped pore structure,facile synthesis and versatile functionality.Therefore,we designed a new pillar[5]arene containing highly reactive functional groups,and obtained a novel POPs based on pillar[5]arene through polycondensation reaction.Then,we explored their performance of gases adsorption and separation and nitro-group explosives adsorption.The specific research contents are as followed:1.Designed and synthesized a new disubstituted 4-formylphenyl pillar[5]arene?FPP5?,and obtain its crystal.And the pillar-shaped structure of FPP5 was seen intuitively from its crystal structure.2.Selected the nitrogen-rich melamine as one of monomers.A pillar[5]arene-based porous polyaminal?PAN-FPP5?was obtained through one-step polycondensation reaction of FPP5 and melamine.For the sake of investigating the effect of the existence of pillar[5]arene on the properties of polymers,FPP5 was replaced by 4,4'-terphenyl dicarbaldehyde?TPDA?,and got another porous organic polymer?PAN-TPDA?.Their chemical structure and thermal stability were characterized by FT-IR spectra,Solid-state ¹³C CP/MAS NMR spectra and TGA.Their pore structures were investigated by nitrogen adsorption test and CO₂ uptake and the selectivity of CO₂/N₂ and CO₂/CH₄ were investigated by the adsorption test of CO₂?CH₄and N₂.The results show that,the polymer PAN-FPP5 containing pillar[5]arene macrocycle indicated a larger specific surface area(S_BET=788.0 m² g^-1),higher CO₂ uptake capacity?12.5 wt%,273 K/1.0 bar?and higher selectivities of CO₂/N₂ and CO₂/CH₄?55.6 and 6.6,298K?,which illustrated the existence of pillar[5]arene has a positive effect on increasing the specific surface area of polymer and enhancing its gas adsorption and separation performance.Finally,their adsorption of explosives capacity were investigated by adsorption of TNP and4-NP,finding polymers show high adsorption efficiency in short adsorption time to lower concentration explosives,expecially for adsorption of TNP,and the adsorption efficiencies for two polymers to 0.05 mM TNP are 93.13%and 94.30%,respectively.We propose that the adsorption of polymers due to the strong intermolecular hydrogen bond interactions between the-NH-group of polymers and-OH group of explosives.