Application Of Pyrene And Perylene-based Conjugated Microporous Polymers In Iodine Adsorption And Fluorescence Sensing Of Nitroaromatic Compounds

With the rapid development of heavy industry in modern society,human beings need more and more clean and efficient energy.At present,the survival and development of human beings consume a lot of energy,which also brings a lot of environmental problems,such as greenhouse effect,water pollution,nuclear leakage pollution and so on.How to solve these urgent problems is the focus of today’s research.Some data show that conjugated microporous polymers have high surface area,high pore structure,high thermal stability and fluorescence.It has been well applied in adsorption and fluorescence sensing.How to design and prepare economic,safe and efficient adsorbents and fluorescence sensors has attracted much attention.In this paper,two conjugated microporous polymers based on thiophene and pyrene,poly[1,3,6,8-tetra（2-thiophenyl）pyrene]and poly[1,3,6,8-tetra（3-thiophenyl）pyrene]（PTThP-2and PTThP-3）,were firstly designed and prepared by FeCl₃ oxidation-coupled polymerization.The structure was analyzed by a series of characterization methods,all of which indicated that the required polymer had been successfully synthesized.Scanning electron microscope（SEM）was used to study the spherical particles with cluster morphology,and the thermal stability of conjugated microporous polymer was tested by thermogravimetric analysis（TGA）.PTThP-2 and PTThP-3 have a considerable BET surface area,exceeding370.8 and 748.2 m² g^-1,with large pore volumes of 0.544 and 0.573 cm³ g^-1,showing good stability and excellent absorbency in iodine vapor,1.62 and 2.00 g g^-1,respectively.In addition,the combination of pyrene and thiophene groups into these polymers can induce high fluorescence in the dispersion of THF,which enables them to detect electron iodine deficiency by fluorescence quenching,with Ksv of 1.99×10³ and 5.09×10³ L mol^-1,and detection limits of 7.54×10^-88 and 2.95×10^-88 mol L^-1,respectively.Secondly,the monomer CPDI was synthesized by 3,4,9,10-perylenetetra carboxylic dianhydride,4-aminobenzonitrile with 1-methyl-2-pyrrolidone as solvent by imination,the synthesis of mesoporous covalent triazine skeleton PCPDI by N,N′-di（4-cyanphenyl）-3,4,9,10-tetracarboxydiimide（CPDI）aromatic nitrile trimerization catalyzed by CF₃SO₃H at 40℃.The measured values obtained by elemental analysis are very close to the theoretical values.The purified polymer network is a fluffy reddish brown powder that is insoluble in water and common organic solvents such as tetrahydrofuran,toluene,dimethylformamide and chloroform.The chemical stability of different aqueous solutions,including HCl and NaOH,is also good.The TGA under nitrogen atmosphere showed that the polymer had good thermal stability,and the weight loss was 5%when approaching 600℃.XRD measurement showed that PCPDI was amorphous and the scanning electron microscope image showed a loose solid.FT-IR showed that triazine ring was formed in PCPDI.In order to monitor the change of theπ-conjugate network,electron absorption spectroscopy was performed.The average pore diameter of the material was 4.69 nm and the specific surface area was 38.0 m² g^-1.PCPDI has good thermal stability and strong fluorescence.PCPDI has shown a high sensitivity to o-nitrophenol in chloroform,with the Ksv constant of 1.74×10⁵ L mol^-11 and detection limit（LOD）of 1.72×10^-1111 mol l^-1.Experiments show that PCPDI can be used as an effective sensing agent for o-NP with high sensitivity.The results show that conjugated microporous polymer is a very promising porous material with good iodine adsorption performance and can be used as a highly sensitive fluorescence sensor for NACs and I₂.