金属-有机框架功能化修饰及吸附重金属性能研究

It is expected to develop adsorbent materials to capture efficiently heavy metal using metal-organic frameworks (MOFs) with most potential materials in this project. MOFs are considered as potential efficient adsorptive materials because of theirs very high surface areas and unique pore structures. However, due to the lack of activity sites on MOFs surface to capture heavy metal, and the shortage of modification methods to improve the removal of heavy metal,the MOFs is restricted to metal pollution control application as adsorbents. The project is synthesizing high stability of the MOFs materials (MIL-101, MIL-53, etc.), and then high adsorption activity groups (sulfonic acid, thiol group, amino group,etc.) will be bonded to benzene ring of MOFs materials. As a result, functionalization of MOFs materials are obtained. Through the micro-structural analysis of functional MOFs materials and heavy metal adsorption properties, optimization of the modified synthesis conditions, and further directed modification are needed to improve heavy metal adsorption properties and adsorptive selectivity. After heavy metal sorption / desorption mechanism are studied, the relational model are established between structures of MOFs functional materials and adsorption properties of heavy metal in order to provide experimental and theoretical basis for the development of MOFs in environmental field as new and efficient adsorption materials.

本项目拟用金属-有机骨架（MOFs）这一最具开发潜力的材料定向研发高效重金属吸附剂。MOFs材料虽具有巨大的比表面积和独特的孔结构，但由于MOFs材料缺乏捕获重金属的活性位点及提高MOFs材料吸附重金属性能的表面活化技术，制约了MOFs材料作为重金属吸附剂在环境污染治理中的应用。本项目将合成稳定性高的MOFs 材料（MIL-101，MIL-53等），再将磺酸根、巯基、氨基等高吸附活性基团键合在MOFs材料的苯环上使其活化，制备功能化MOFs材料；通过对功能化MOFs材料的微结构分析及对重金属吸附性能研究，优化改性合成条件和进一步对吸附剂进行定向修饰，提高MOFs材料对重金属的吸附性能和吸附选择性，使其成为高效重金属吸附材料；通过对重金属吸附/解吸机理研究，建立功能化MOFs 材料结构与重金属吸附性能之间的关系模型，为新型高效吸附材料的开发奠定实验和理论依据。

本项目成功合成了磺酸基修饰的金属-有机框架、金属双膦酸盐金属-有机框架、锌次膦酸金属-有机框架和铝金属配位聚合物等金属-有机框架材料，并对合成金属-有机骨架进行了单晶衍射、粉末衍射、元素分析、红外光谱、扫描电镜、比表面积分析和热重分析等表征。同时对金属-有机框架进行吸附实验测试，合成的金属-有机骨架对水溶液的污染物具有较高的吸附能力。研究了污染物浓度、吸附时间、溶液pH、吸附温度、投加量、盐离子溶度等因素对吸附的影响。对吸附热力学用Langmuir、Freundlich等模型进行拟合；对吸附动力学用伪一级动力学、伪二级动力学及粒子扩散方程进行拟合。拟合实验结果表明：金属-有机骨架对污染物吸附质的吸附等温线均能较好的用兰格缪尔单层吸附理论拟合，吸附动力学符合伪二级动力学方程，吸附活化能数据表明吸附过程为一个自发的物理吸附过程，不同结构的金属-有机骨架对污染物吸附差异较大。