Fe-TAML键合环糊精分子反应器构建及其选择性降解微污染物

Micropollutants are ubiquitously detected at low levels (ng/L-μg/L) in aquatic systems, comprising thousands of pesticides, antibiotics, PPCPs, and their transformation products. Many micropollutants cause largely long-term adverse effects, challenging aquatic systems and human health. Various unit processes (e.g., adsorption, oxidation, and biological degradation) and combinations of these processes have been developed to remove organic pollutants (mg/L-g/L) in wastewater. However, they often fail to remove aqueous micropollutants with poor selectivity and low efficiency, because of the interference of natural water components that are 3-9 orders of magnitude more concentrated. Therefore, discovering water treatment technologies of good selectivity and high efficiency is one of key scientific issues for the mitigation of micropollutants in aquatic systems. ..This study is aimed at discovering newly supramolecualr metalloenzyme-like catalysts, containing tetraamidomacrocyclic ligand iron (Fe-TAML) function centers and cyclodextrin (CD) skeletons. The idea to discover such catalysts is created in interdisciplinary crossing of Supramolecular Chemistry and Metalloenzyme Chemistry, both of which provide host compounds (e.g., CD) and metalloenzyme-like catalysts (e.g., Fe-TAML), respectively. CD and Fe-TAML will be covalently conjugated by chemical methods, ensuring chemical stability of the catalysts (i.e., Fe-TAML-CD). Fe-TAMLs, well-known CYP P-450- and Peroxidase-like catalysts, can activate hydrogen peroxide to destruct many pollutants. Cyclodextrins are widely recognized host compounds, characterized by a toroidal shape with a hydrophobic inner cavity and hydrophilic external surface, and their cavities can reversibly encapsulate size-matched guest compounds in the molecular level. So the catalysts may be used to construct newly molecular reactors for the removal of aqueous micropollutants, in which organic pollutants in natural waters will be selectively captured by CD cavities and then be catalytically destructed by the Fe-TAML centers. ..In this study, a variety of Fe-TAML-CD-based molecular reactors will be synthesized by selective substitution reactions between Fe-TAMLs and CDs. Detailed research will be carried out to investigate destruction efficiency of the reactors toward the concerned miropollutants, to reveal working principles of the reactors, and to develop mathematical models of destruction efficiency of the reactors related to chemical structures and properties of micropollutants. Finally, units of the molecular reactors will be designed to destruct micropollutants in natural waters. This study is expected to provide new ideas for the development of micropollution control technologies.

微污染物在水环境中被普遍检出，它们种类多、浓度低、潜在风险大，是水生生态安全与人类健康的重大挑战。水中天然组分干扰常规水处理技术对微污染物的降解去除过程，导致污染物去除的选择性差、效率低。因此，选择、高效的污染控制原理与技术是水体微污染领域的科学难题。本项目通过超分子化学与金属酶化学学科交叉，拟开发新型超分子金属类酶催化体系，将具有类酶催化活性的Fe-TAML共价键合到具有超分子识别功能的环糊精空腔骨架上，制备Fe-TAML键合环糊精及功能材料，可利用环糊精空腔选择性结合与捕捉水中微污染、利用Fe-TAML催化降解所捕捉的微污染物，构筑具有高选择性、高催化降解活性的Fe-TAML键合环糊精分子反应器。将考察该分子反应器对水体中农药、抗生素等微污染物的催化降解性能，揭示其催化反应机理，构建其催化降解效率的的数学模型，尝试将其装置化用于实际水体微污染控制。研究成果预计将为微污染控制提供新思路。

水体中有机微污染物种类繁多，浓度水平低(ng/L-μg/L)。水体中广泛存在的天然组分，浓度通常是微污染物浓度的10^3-10^9倍，干扰有机污染物的降解去除。常规水处理技术由于缺乏选择性难以有效去除微污染物，亟需开发高效高选择性的水处理技术。本研究采用有机合成手段成功制备了Fe-TAML催化剂和环糊精-Fe-TAML键合型催化剂，构建了Fe-TAML键合环糊精均相催化体系及功能材料非均相催化体系。. 基于Fe-TAML/H2O2体系在不同pH值条件下对微污染物的降解速率和污染物结构参数、量子化学参数及催化剂解离形态分布参数，建立了Fe-TAML对微污染物的催化降解性能的预测模型。阐明了Fe-TAML催化剂先与污染物发生弱结合、再被活化生成高价铁活性物种、然后氧化降解污染物的反应机理。该反应机理解释了Fe-TAML/H2O2体系不受水体组分的干扰。Fe-TAML键合环糊精的水解稳定性及氧化稳定性明显提高。Fe-TAML键合环糊精对啶虫脒、磺胺嘧啶等特定结构的微污染物的催化降解性能和催化剂的稳定性均显著高于单独Fe-TAML体系和Fe-TAML/环糊精混合体系。揭示了Fe-TAML键合环糊精通过环糊精的包合作用和结构优化等作用影响了Fe-TAML催化剂的催化活性及稳定性。采用交联聚合手段制备了具有球形结构的Fe-TAML键合环糊精的交联聚合物功能材料（Fe-TAML-CDP）和具有多孔块状结构的Fe-TAML-MgO-CDP复合材料。Fe-TAML-CDP材料对氯酚类污染物降解去除性能高，可循环利用30次以上。Fe-TAML-MgO-CDP材料能够缓慢释放Fe-TAML，可作为Fe-TAML的缓释材料；材料中MgO可以提供碱性环境，使材料具有较好的pH适用性（3-12），能处理酸性和中性水体。