Synthesis And Adsorption Performance Of Nitrogen And Oxygen Functionalized Hyper-Crosslinked Polymers

Hyper-crosslinked polymers（HCPs）are widely used in the adsorption and removal of organic pollutants in wastewater,due to their advantages of large specific surface area and special pore structure.Functionalized hyper-crosslinked polymers are one of the current research hotspots.In this paper,three types of functionalized HCPs are designed and synthesized using chloromethylated polystyrenes（CMPs）as raw materials,and their removal of small molecular organic pollutants in aqueous solutions is systematically studied.The specific research content and results are as follows:（1）Using CMPs as raw material,by nucleophilic substitution reaction,the polymers precursor PS-BA is prepared by loading benzoic acid（BA）on the surface of CMPs.Then,using dimethoxymethane（FDA）as external cross-linking agent,Friedel-Crafts alkylation under H₂SO₄or anhydrous Fe Cl₃.Carboxyl-functionalized HCPs:PS-BA-HCPs-1 and PS-BA-HCPs-2 are prepared,respectively.The experimental results show that PS-BA-HCPs-1 has higher specific surface area S_BET（460 m²/g）and pore volume V_total（0.53 cm³/g）.The adsorption results show that PS-BA-HCPs-1 has a better adsorption effect on aniline.its maximum equilibrium adsorption capacity reaches 201.5 mg/g,and the adsorption equilibrium can be reached in about 80 min,better than most reported.In addition,aniline in the molecular state is more favorable for its adsorption,and after 5 adsorption-desorption cycles,the polymers still has good adsorption performance.（2）Using CMPs as raw materials,by nucleophilic substitution reaction,introducing 1,5-dihydroxynaphthalene（NP）on the surface of CMPs to prepare the polymers precursor PS-NP.The further step uses different external crosslinkers in the Friedel-Crafts alkylation reaction:FDA,cyanuric chloride（CC）,1,2-dichloroethane（DCE）,4,4’-dichloromethyl linker Benzene（BCMBP）and 1,4-p-dichlorobenzyl（DCX）,and five types of oxygen functionalized HCPs are prepared.Structure shows,among them,PS-NP-DCE has the highest S_BET（727m²/g）and V_total（0.66 cm³/g）.4-nitroaniline（4-NA）is proposed to be used as the adsorbate.The adsorption of 4-NA by these materials is studied.The experiment show that PS-NP-DCE has the maximum equilibrium adsorption capacity for 4-NA（460 mg/g）,in which acid-base interaction,hydrogen bonding and micropore filling mechanisms are the main driving forces for the adsorption of 4-NA.In addition,the polymers also exhibit good reusability,and after 5 adsorption-desorption cycles,still has good adsorption performance.（3）Using CMPs as raw materials,one-step nucleophilic substitution reaction under solvent conditions such as N-methylpyrrolidone（NMP）,DMF,and acetone（ACE）.A kind of triazine based HCPs:PS-OH-NMP,PS-OH-DMF and PS-OH-ACE are synthesized by inserting 2,4,6-tris（4-hydroxyphenyl）-1,3,5-triazine into the framework of CMPs.The results show that the solvent has a significant effect on the reaction,and the pore structures of the prepared HCPs are greatly different.The polymers PS-OH-NMP prepared with NMP as solvent is dominated by micropores and higher S_BET（367 m²/g）and V_total（0.48 cm³/g）.The pores of the other two HCPs are mainly mesoporous/microporous.The adsorption results show that PS-OH-NMP has a good adsorption effect on4-nitrophenol（4-NP）,its maximum equilibrium adsorption capacity reaches 384.91 mg/g,which is better than most of the reported literatures.In addition,the molecular state of 4-NP is more favorable for its adsorption,and the polymers after five adsorption-desorption cycles,still has good adsorption performance.