| Nuclear energy is deemed as one of the best alternative energy sources to fossil fuels due to its features of low greenhouse gas emissions and high energy density.Nevertheless,radioactive volatile iodine generated from the reprocessing the used nuclear fuel and the nuclear accident,threatens to human health and the global environment.Solid phase adsorption is regarded as the primary choice for removal radioactive iodine due to its general applicability,high removal efficiency,simple and fast operation procedure as well as inexpensive cost.Various solid adsorbents such as silver-exchanged zeolites,chalcogen-based aerogels,metal organic frameworks,and porous organic polymers（POPs）have been explored to capture iodine.Among them,POPs have remarkable advantages such as excellent physical/chemical stability,low skeleton densities,high surface area as well as tunable pore size and functionality.As a subset of POPs,hyper-cross-linked polymers（HCPs）not only inherit the merits of POPs,but also have their distinguish virtues,such as diverse synthetic methods,facile operation conditions,and low-cost reagents.However,HCPs made up solely of light atoms（e.g.,carbon and hydrogen）have low affinity to iodine,which hinders their application as solid adsorbents in the field of iodine capture.Based on the interactions between lone pair electrons on heteroatoms and iodine molecules,the incorporation of heteroatoms into the framework of HCPs has a positive effect on iodine capture.Therefore,the aim of the present study is to construct various heteroatoms-containing HCPs and their applications in the field of iodine capture.The detailed contents are as follows.1.Poly（ethyleneimine）impregnated HCPs were prepared by a simple wet impregnation method and employed as adsorbents for removal iodine.Owing to high nitrogen content,?-conjugated structure,and large surface area,the resultant materials exhibited highest iodine uptake capacity up to 607 wt%.Spectra studies indicated that the iodine adsorption sites were N–H units as well as aromatic rings and the form of iodine was polyanions.Furthermore,the material could be reused,which was beneficial for its practical applications.2.Viologen-based HCPs were prepared via a one-pot method for capture iodine in both vapor and solution phases.Thanks to the viologen units in the skeletons,the viologen-based HCPs were simultaneously doped with two kinds of iodine affinity sites,e.g.,nitrogen species and charged sites.The iodine uptake capacities increased with increasing amount of viologen units in polymers with a maximum capacity of525 wt%.The capture mechanism and the release performance of adsorbed iodine in ethanol were studied.Besides,the adsorption performance of iodine in solution phase was also evaluated.3.A phenyl-bearing triazine-based monomer,2,4,6-triphenyl-1,3,5-triazine（TP3）,was firstly prepared,after which TP3 and pyrrole were copolymerized to prepare a triazine and pyrrole bifunctionalized HCP.The nitrogen-enriched adsorbent had an uptake capacity for iodine of 257 wt%.The process of iodine adsorption occurred at triazine,pyrrole,and phenyl ring units and the form of adsorbed iodine was polyanions.The process of iodine capture was reversible and the adsorbed iodine could be released either immersing in organic solvents or upon heating.Besides,the performance of iodine adsorption in solution phase were also evaluated.4.An electron-enrich thiophene-based HCP was prepared by using thiophene and perylene as comonomers.By combination of the features of high sulfur content,?-conjugated structure,and high porosity,the adsorbent could capture iodine of 360wt%,which was the highest value among the reported thiophene-based POPs.The capture mechanism and the release performance of adsorbed iodine in organic solvent were also studied.Besides,the adsorption isotherm,kinetics,and thermodynamics in solution phase were investigated.5.A sulfur-doping monomer,hexakis（benzylthio）benzene with twisted structure,was firstly prepared,after which the sulfur-doping monomer and thiophene were copolymerized to construct hyper-cross-linked polymer nanosheets（HCP NSs）and nanotubes（HCP NTs）with large surface areas and high sulfur contents.A facile solvent-induced polymerization method of constructing ultrathin free-standing two-dimensional porous nanosheets was reported.In this work,chloroform was used as not only solvent but also crosslinker to dedicate the degree of polymerization.The morphology of resultant porous polymers could be easily changed from nanosheets to nanotubes by increasing the amounts of chloroform.HCP NTs with larger surface area and higher sulfur content displayed a guest uptake of 270 wt%in iodine vapor and could adsorb iodine with an uptake of 303 mg g-1 in solution phase. |
