Synthesis And Application Of Pyridine-based Ionic Porous Organic Polymers

Porous organic polymers(POPs)are a kind of porous materials with high porosity and good stability.At the same time,the abundant pore structure also provides a broad contact interface for POPs to interact with external molecules.These characteristics make POPs receive extensive attention in the field of materials science.In recent years,ionic porous organic polymers(IPOPs),as a branch of porous organic polymers,have also developed to some extent.IPOPs are new porous polymers bonded by chemical bonds.They not only have the advantages of POPs,but also have the characteristics of charged ionic compounds.So far,the synthesis of ionic porous organic polymers can be roughly divided into four methods,including(1)the direct polymerization of ionic building units,(2)the copolymerization of ionic building units and neutral monomers,(3)the polymerization of neutral monomers along with the subsequent ionization,and(4)introducing the ionic building units into the polymeric networks by a post-synthesis modification strategy.These strategies have afforded a variety of IPOPs for many applications.However,until now,most reported IPOPs generally show undesirable porosity with the low Brunauer-Emmett-Teller(BET)specific surface areas,which largely limit the application of IPOPs in many fields,especially in adsorption and heterogeneous catalysis.Therefore,it can be inferred that IPOPs are difficult to obtain both high BET specific surface area and high ionic density by direct polymerization.Therefore,the preparation of IPOPs with both great porosity and preferable ionic density is still challenged.Based on the above research status,in this paper,IPOP-1,IPOP-2,IPOP1-XL,and IPOP2XL were prepared through quaternary ammonium reaction and Friedel-Crafts reaction,and used in the thermal catalysis of carbon dioxide(IPOP1-XL)and the adsorption of heavy metal ions(IPOP-2).The specific research content is as follows:1.The preparation of IPOP-1 and IPOP-2 and the study on their adsorption properties for Re O₄^–.IPOP-1 and IPOP-2 were first synthesized by the quaternizationreactionofcyanuricchloride(Cy C)with2,4,6-tri(4-pyridyl)-1,3,5-triazine(TPT)or 1,3,5-tri(pyrid-4-yl)benzene(TPB).IPOP-2 not only has abundant cationic active sites but also has good ionic exchange ability,so IPOP-2 can be used as a good adsorbent for removing radioactive waste Re O₄^–.Experiments have proved that IPOP-2 has a high adsorption capacity(400.9mg g^-1),ultra-fast kinetics and excellent selectivity,and high adsorption stability at different p H values.Notably,it can still maintain high selectivity in the presence of high concentrations of SO₄^2–or NO₃^–,even reaching a high selectivity of 79%in a solution with 100 times excess SO₄^2–.2.The preparation of IPOP1-XL and IPOP2-XL and the study of their catalytic performance for CO₂cycloaddition reaction.IPOP1-XL and IPOP2-XL were synthesized by quaternary ammonium reaction and Friedel-Crafts reaction with?,?'-dichloro-p-xylene(DCX)in the presence of Fe Cl₃by IPOP-1 or IPOP-2 to solve the problem of the low specific surface area of IPOPs.Especially,IPOP1-XL exhibits a large Brunauer-Emmett-Teller(BET)specific surface area of 1830 m~2g^-1,which is 19 times of IPOP-1(96 m~2g^-1).The uptake capacity for carbon dioxide(CO₂)of IPOP1-XL(11.7 wt%)is significantly higher than that of IPOP-1(4.5 wt%)at 273 K due to the increase of porosity.Meanwhile,IPOP1-XL also possesses a desirable ionic density(3.5 mmol g^-1),which plays a pivotal role in CO₂chemical fixation.The experimental results show the catalytic efficiency of most epoxides can reach more than 99%by using epoxides as the substrates in the presence of Tetrabutylammonium bromide(n-Bu₄NBr)cocatalyst at 35°C under atmospheric CO₂pressure.