摘要
具有高比表面积及规则孔道结构的离子型共价有机框架(COF)材料表现出广泛的应用前景.本文设计合成了一种基于联吡啶嗡盐的阳离子型COF材料(PS-COF-1).PS-COF-1比表面积为2703 m^(2) g^(-1),高于目前报道的其他离子型COF材料.PS-COF-1具有固定的一维通道(~4.5 nm)、良好的化学稳定性和耐辐照稳定性,表现出优异的吸附ReO_(4)^(-)(最大吸附量为1262 mg g^(-1))和^(99)TcO_(4)^(-)性能.进一步研究表明,PS-COF-1在高离子强度下表现出快速吸附动力学、高吸附容量和对^(99)TcO_(4)^(-)和ReO_(4)^(-)的高选择性,在模拟美国汉福德低活性废物流条件下成功选择性去除了^(99)TcO_(4)^(-).此外,PS-COF-1能够在10 min内将ReO_(4)^(-)和^(99)TcO_(4)^(-)污染水净化至饮用水级别.密度泛函理论计算表明,PS-COF-1对低电荷密度阴离子ReO_(4)^(-)和^(99)TcO_(4)^(-)具有强的亲和力(优于其他常见阴离子,如Cl^(-),NO_(3)^(-),SO_(4)^(2-),CO_(3)^(2-)),阐明了PS-COF-选择性吸附^(99)TcO_(4)^(-)的机理.本文展示了一种用于选择性捕获放射性核素新型阳离子COF吸附剂,为放射性污染治理提供了重要的理论依据和指导.
Ionic covalent organic framework(COF)materials with high specific surface areas and well-defined pore structures are desired for many applications yet seldom reported.Herein,we report a cationic pyridinium salt-based COF(PS-COF-1)with a Brunauer-Emmett-Teller(BET)surface area of 2703 m^(2) g^(-1),state-ofthe-art for an ionic COF.Aided by its ordered pore structure,chemical stability,and radiation resistance,PS-COF-1 showed exceptional adsorption properties toward aqueous ReO_(4)^(-)(1262 mg g^(-1))and ^(99)TcO_(4)^(-).Its adsorption performance surpassed its corresponding amorphous analogue.Importantly,PS-COF-1 exhibited fast adsorption kinetics,high adsorption capacities,and selectivity for ^(99)TcO_(4)^(-)and ReO_(4)^(-)at high ionic strengths,leading to the successful removal of ^(99)TcO_(4)^(-)under conditions relevant to low-activity waste streams at US legacy Hanford nuclear sites.In addition,PS-COF-1 can rapidly decontaminate ReO_(4)^(-)/^(99)TcO_(4)^(-)polluted potable water(~10 ppb)to drinking water level(0 ppb,part per billion)within 10 min.Density functional theory(DFT)calculations revealed PS-COF-1 has a strong affinity for ReO_(4)^(-)and ^(99)TcO_(4)^(-),thereby favoring adsorption of these low charge density anions over other common anions(e.g.,Cl^(-),NO_(3)^(-),SO_(4)^(2-),CO_(3)^(2-)).Our work demonstrates a novel cationic COF sorbent for selective radionuclide capture and legacy nuclear waste management.
基金
supported by the National Natural Science Foundation of China(U2167218 and 22006036)
the National Key Research and Development Program of China(2017YFA0207002 and 2018YFC1900105)
the Science Challenge Project(TZ2016004)
the Beijing Outstanding Young Scientist Program(H.Y.and X.W.)
the Robert A.Welch Foundation(B-0027)(S.M.)。
