用于二氧化碳捕获的微孔聚席夫碱合成、原位化学改性及结构性能关系研究

Microporous polymers with pore size smaller than 2 nm show great potential in CO2-capture because of their considerable surface area and environmental stability. In the present project, at first, wholly aromatic microporous poly(Schiff base)s with systematically varied structures will be synthesized. Then, the imine C=N groups are in-Situ reduced to create microporous polymers with pore walls occupied by large amount of secondary amines (C-NH). The correlations between CO2 adsorption and porous structures before and after chemical modification will be studied. The project aims at exploring novel approach to functionalized microporous polymers via in-Situ conversion of active groups, and providing the theoretical and experimental bases for the development of microporous polymers for CO2-capture. The main research contents lie in three aspects:.(1).Nine poly(Schiff base)s are designed and will be synthesized via polycondensation method by using tetrakis(4-aminophenyl)silane, tris(4-aminophenyl)amine and 1,3,5-tris(4-aminophenyl)benzene to react with p-dialdehydebenzene, p-dialdehydebiphenyl, and m-dialdehydebenzene, respectively. The polymerization conditions such as medium, concentration and time are optimized. The structures, thermal stability and pore morphologies are characterized by solid FTIR and 13C CPMAS NMR spectra, WAXD, SAXS, TGA, SEM and TEM methods. The BET surface areas and pore size distributions are obtained through the isothermal nitrogen adsorptions. The effects of structure, pore distribution and specific surface area of polymers on CO2 adsorptions will be studied. .(2).Under the optimized condition, the polymerization processes, including the oligomerization, branching, hyperbranching, and the eventual formmation of crosslinking network, will be dynamically followed by real-time FTIR, 13C NMR, 29Si NMR, MALDI-TOF MS, elemental analysis and GPC methods. The chemical and topological structures of intermediate products at various stages are analyzed. The results will be of significance for elucidating the construction mechanism of microporous polymers and understanding the effects of geometric configuration of building blocks on the topological structures of hypercrossloninked networks..(3).More importantly, the C=N imine groups in the mciroporous poly(Schiff base)s will be in-Situ converted into secondary amines. The newly created microporous polymers are expected to significantly enhance CO2 adsorption because of the strong affinity of C-NH groups for CO2. The effects of reaction conditions such as reduction agent, medium, concentration, temperature and time on the reduction degree and the content of secondary amine groups generated within the polymer network will be examined. The variations of specific surface area, pore size and distribution, CO2 adsorption and its selectivity over H2, N2 and CH4 gases for the microporous polymers before and after chemical modification will be investigated in detail.

有机微孔聚合物（孔径小于2nm）具有巨大比表面积和优异的环境稳定性能，在CO2捕获材料领域显示出良好的前景。本项目拟采用刚性四面体、三角锥和平面三角形构型的四(4-氨基苯基)硅烷、三(4-氨基苯基)胺和1,3,5-三(4-氨基苯基)苯分别与对苯二甲醛、间苯二甲醛和联苯二甲醛聚合，制备系列结构的微孔聚席夫碱，研究基元几何构型对微孔聚合物网络拓扑结构形成过程的影响以及聚合物微孔形貌参数变化与CO2气体吸附性能的内在联系。此外，利用聚席夫碱网络中含有大量易被还原的C=N亚胺基团结构特点，选择合适的还原条件将微孔孔道上部分或全部亚胺基团定点还原为对CO2亲和性更强的仲胺基团（C-NH），系统研究还原前后材料比表面积、孔径尺寸和孔径分布的变化规律，揭示孔道微化学环境和孔形貌参数变化对CO2吸附性能协同作用机制，制备出新型高效CO2捕获材料，为今后设计合成微孔聚合物CO2捕获材料提供理论和实验依据。

本项目按研究计划进行，圆满完成预定目标。已在Journal of Materials Chemistry A, Chemical Communications, Macromolecules, polymer Chemistry, Journal of Physical Chemistry C等高水平国际学术期刊上发表SCI论文19篇，还有多篇论文将随后整理出版。.主要创新性结果如下：.（1）1, 3, 5, 7-四（4-醛基苯基）金刚烷和对苯二胺和间苯二胺、1, 3, 5, 7-四（氨基苯基）金刚烷、四（4-氨基苯基）甲烷、1, 3, 5-三（4-氨基苯基）苯及三（4-氨基苯基）胺在“A4+B2/B3/B4”聚合体系中合成了系列微孔聚席夫碱PSNs；连接单元的结构导向作用对PSNs的孔道结构具有重要影响，扭曲的PSN-1交联网络具有0.72 nm左右的微孔结构并表现出较高的BET比表面积1045 m2/g，其余PSNs的BET比表面积为419-865 m2/g；聚合物还表现出良好的CO2吸附能力及选择性，在273 K和1 bar条件下CO2吸附量介于6.7-15.0 wt%，CO2/N2、CO2/CH4分离比最高分别达到85.3和15.8。.（2） 将1, 3, 5, 7-四（4-醛基苯基）金刚烷与三氨基嘧啶(PTA)和2, 4, 6-三氨基三嗪单体(TTA)聚合，氨基的高活性使网络中-C=N-可原位转化为缩醛胺-HN-CH-NH-链节。所得聚合物的BET比表面积高达1242 m2/g，孔径集中于0.52 nm超微孔范围。含有大量仲胺及氮杂环结构的聚缩醛胺骨架也表现出优异的CO2亲和能力，在273 K和1 bar条件下, CO2吸附量高达17.6 wt%，CO2/N2、CO2/CH4选择性分别达到104.3和23.8，优于大多数微孔聚合物。.（3）利用TTA与苯甲醛、4-氟苯甲醛、4-甲基苯甲醛、4-三氟甲基苯甲醛、2-呋喃甲醛、2-噻吩甲醛聚合，得到了系列富含-HN-CH-N-仲胺基团的比表面积介于615-907 m2/g的微孔聚缩醛胺，氟原子、呋喃、噻吩、萘环及芘环结构单元的引入使得微孔网络的CO2吸附量及选择性显著提高，噻吩基PAN-6在273 K和1 bar条件下CO2吸附量达到14.8%；PANs也具有良好的CO2/N2及CO2/CH4选择性。