Preparation And Application Of Soluble Polymers With Intrinsic Porosity

Polymer of intrinsic microporosity(PIMs)relies on their own rigidity and nonplanar twisted structure of molecular chains to obtain microporosity and high specific surface area.They also have good thermal and chemical stability and solution processability.Thanks to the above unique characteristics,they are widely used in gas separation,catalysis,hydrogen storage and so on.With economic development and technological progress,the increasing demand for functionalization of materials,and even one material needs to have multiple functions simultaneously.The purely organic nature and excellent properties of PIMs offer the possibility of multifunctionality.In this dissertation,a soluble polymer of intrinsic microporosity(PIM-1)was synthesized by high-temperature polymerization.Then it was applied to the removal of phenolic compounds in wastewater,and the robust sensitive detection of iodine vapor.The works done in this dissertation opened up new windows of applications of PIMs in terms of solving environmental problems.The main research contents are as follows.1.Efficient removal of organic phenols from phenolic wastewater was achieved,and the long-suffering issue of adsorbents fouling and regeneration after blocking has been solved.Adsorption is an important technology for wastewater treatment.The existing adsorbents are mainly non-soluble porous materials such as graphite.Although they can provide good adsorption capacity and adsorption kinetics,the adsorption process is inevitably contaminated or clogged,resulting in a rapid decline in adsorbent performance and difficult to regenerate,In consequence,the operation cost was greatly increased along with generation of large amounts of solid waste.PIM-1 is resistant to water and protic solvents like methanol but well soluble in some organic solvents such as chloroform and methylene chloride.Taking the advantage of which,a good solvent dissolution-filtration-non solvent precipitation strategy has been developed which can well overcome the above mentioned problems.The blockage can be released by dissolving after it was blocked.In addition,PIM-1 demonstrates comparable adsorption capacity to the state-of-the-art phenolic pollutant adsorbents,and is capable of selectively and rapidly adsorbing phenolic compounds to a concentration below the safety standard for drinking water.Density functional theory(DFT)calculation revealed a strong affinity between the cyano groups of PIM-1 and the phenoxy group of phenols due to hydrogen bonding.The phenolics can be selectively adsorbed over a range of pH values.This work provides a theoretical and experimental basis for the use of soluble organic polymers as adsorbents.2.A robust off-on-line fluorescent gaseous iodine detection film sensor has been successfully fabricated and applied.In nuclear fuel reprocessing or in case of nuclear accidents,rapid and sensitive detection of radioactive iodine and issuing early warnings are of extreme importance for the safety of the population and the environment.PIM-1 was found to be highly fluorescent and this fluorescence can be efficiently and rapidly quenched by iodine vapor.Based on this,we prepared PIM-1 films and achieved highly sensitive detection of iodine vapor using fluorescence sensing.In the fluorescence offline detection,the fluorescence intensity of the self-supporting PIM-1 film decreased dramatically after exposure to iodine vapor.Even a few ppb iodine vapor could cause almost complete quenching of fluorescence of the film within 5 minutes,without being altered by H2O,CO2 or H2S.A portable fluorescence detection device has also been developed which was used for online real-time detection of gaseous iodine.For which purse,PIM-1 film was cast onto the inner surface of a capillary tube that allows iodine contaminated flue gas to pass through.The fluorescence intensity was constantly measured and a sharp drop could be observed once iodine gas was touched.Theoretical calculations show that the iodine molecule interacts with the fluorescent chromophore of PIM-1,the lowest unoccupied molecular orbital(LUMO)of iodine is close to but a little lower than the LUMO of PIM-1.Thus the excited electrons of PIM-1 easily leap to the iodine molecule and undergo fluorescence quenching.At the same time,the high porosity and inherent porosity of PIM-1 facilitate the adsorption of iodine vapor,hence resulting in high sensitivity.