Preparation And Properties Of Spirofluorenyl And Pyrazinyl Conjugated Microporous Polymers

Radioiodine ¹²⁹I and ¹³¹I can be used for medical diagnosis and treatment,and because of their radiation harm to human body and environment is also quite large.How to detect and capture radioiodine effectively has become the focus of scientific researchers.Nitro aromatic compounds（NACs）are a kind of synthetic rather than naturally generated compounds,which are raw materials of various industrial products.Even if several concentrations of NACs are very low,they will combine to produce toxicity.Therefore,how to detect the low concentration of NACs in the environment efficiently is particularly important.The results show that microporous materials have high heat resistance,high BET specific surface area and large pore volume due to their special structure,so they show advantages in many industrial and academic applications,such as heterogeneous catalysis,gas storage,chemical separation and sensing.Based on this background,we synthesized four organic conjugated microporous polymers（CMPs）TS-TAD,TS-TADP,TDTPAPz and TTDPz.First,using CH₃SO₃H as catalyst,two spirobifluorene-based fluorescent conjugated microporous polymers TS-TAD and TS-TADP with amorphous structure were prepared by Friedel-Crafts coupling reaction.They have excellent chemical stability,are stable in water and common organic solvents,and are stable in 3 mol/L HCl solution or 3 mol/L NaOH solution.Both CMPs are stable at higher temperatures.PXRD proved that these polymers are amorphous and do not exhibit long-range crystallization order.Scanning electron microscope images revealed the morphology of TS-TAD and TS-TADP,which are composed of aggregated particles with different morphologies,shapes and sizes.The BET specific surface areas of TS-TAD and TS-TADP are 828 and 783 m2/g,respectively,and the pore volumes are 1.51 and 0.54cm3/g,respectively.TS-TAD and TS-TADP have iodine vapor absorption capacities as high as 4.15 and 3.65 g/g,respectively.Simultaneously,iodine adsorption-desorption experiments of two polymers in cyclohexane（CHA）solution were performed,which showed that they have reusable properties.The potential applications of TS-TAD and TS-TADP as fluorescent sensors for electron-deficient iodine,o-NP and PA were also investigated.TS-TAD and TS-TADP have good linear Stern-Volmer relationships for I₂,O-nitrophenol（o-NP）and 2,4,6-trinitrophenol（PA,also known as picric acid）.The Ksv values of I₂,o-NP,and PA increased from 10³ to10⁴ L/mol,and the detection limits for I₂,o-NP,and PA of TS-TAD and TS-TADP were 10^-9 to 10^-12 mol/L,which means that TS-TAD and TS-TADP have high sensitivity to I₂,o-NP and PA.Through Friedel-Crafts alkylation reaction,2,5-ditriphenylaminopyrazine（DTPAPz）and N,N,N’,N’-tetraphenyl-2,5-（diazyl）pyridine As a synthetic monomer,TDPz was reacted with 2,4,6-trichloro-1,3,5-triazine（TCT）,and two pyrazinyl groups were prepared using methanesulfonic acid as a catalyst.CMPs materials are TDTPAPz and TTDPz.The thermal stability of the two compounds is very good,and the decomposition temperatures in nitrogen atmosphere are above 596 and 248°C,respectively.Utilizing the porous morphology,electron-donating nitrogen,and electron-rich conjugate structure,CMPs have very good absorption of iodine vapor,reaching 4.41 and 3.12 g/g,respectively.The recoverability test results show that even after three adsorption-desorption cycles,TDTPAPz and TTDPz can maintain about 80%and 90%iodine capacity.In addition,the fluorescence quenching coefficients Ksv of the two CMPs for electron-deficient iodine,o-NP,and PA reached 10³ L/mol,which indicates that the two types of CMPs have a higher effect on o-NP,PA,and I₂.