【作者】 黄小鲜；

【导师】 裘灵光；

【作者基本信息】 安徽大学 ， 物理化学， 2012， 硕士

【摘要】 金属-有机骨架材料(Metal-Organic Frameworks MOFs)是指过渡金属离子与有机配体通过自组装形成的具有周期性网络结构的晶体多孔材料。它具有高孔隙率、低密度、大比表面积、孔道规则、孔径可调以及拓扑结构多样性和可裁剪性等优点。在气体存储及分离、催化、离子交换、吸附、传感器以及光、电、磁等领域具有广阔的潜在应用前景。近年来,MOFs材料的设计合成、结构及性能研究已经成为活跃的研究领域之一,并受到各界科研工作者们的广泛关注。文献已报道的MOFs多为微孔材料体系,微孔MOFs材料的孔道比较窄,阻碍了大分子扩散和传质过程,这使得微孔MOFs材料的广泛应用受到限制。随着MOFs材料应用领域的不断拓展,对其性能要求也在不断提高,设计制备介孔或大孔MOFs材料己成为MOFs研究领域的挑战之一。科研工作者们依据分子工程学和晶体学原理提出了多种解决方案,其中,解决方案之一是合成结构复杂的、尺寸更大的有机配体与金属离子自组装成具有介孔或大孔结构MOFs材料,但这类MOFs材料自身不够稳定,当移除客体分子(如：溶剂分子)容易造成孔道坍塌,如何选择刚性的、合适的有机配体成为主要的困难和挑战。于此同时,围绕对已有文献报道的微孔MOFs材料进行修饰和功能化研究工作也受到了人们越来越多的关注。其中,结构调控剂辅助制备多级结构MOFs材料的合成方法已经得到了科研工作者认可。该方法是将表面活性剂分子形成的胶束作为模板即结构调控剂引入到微孔MOFs合成过程中,当移除软模板时,MOFs材料中既保留原有的微孔结构又会形成介孔或大孔的结构。采用该方法制备的MOFs材料具有微孔、介孔甚至大孔共存的多级结构,此外,MOFs多级结构中的微／介／大孔比例分布大小可以通过引入不同结构调控剂的种类进行调整而达到人们预期设想。依据这一策略已经成功地合成了多级结构的Cu(BTC)、MIL-101等MOFs材料。分子在多级结构MOFs材料中的扩散传质过程与在微米尺度MOFs晶体中传质是完全不同的,它具有接触面积大、扩散速度快和传质路程短等特点。这些特性促使多级结构MOFs材料在分子吸收和分离、催化方面具有巨大的潜在应用价值。在本论文中,我们利用表面活性剂作为结构调控剂制备了纳米多级结构MOFs材料,同时研究纳米多级结构MOFs材料在染料吸附和光催化降解方面的应用。其主要内容如下：1、选择阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)作为超分子模板和1,3,5-三甲苯(TMB)作为助模板剂水热合成了多级孔道MIL-101(Cr3F(H2O)2O[(O2C)-C6H4-(CO2)]3.nH2O),考察了不同CTAB和TMB用量与多级孔道MIL-101形貌和尺寸的关系,并用粉末X-衍射(PXRD)、扫描电镜(SEM)、透射电镜(TEM)和氮气吸脱附测试对多级孔道MIL-101结构、形貌、比表面积和孔性质进行了表征。同时,考察了多级孔道MIL-101与MIL-101微晶对染料分子次甲基蓝(MB)的吸附效果对比试验,结果表明多级孔道MIL-101对MB具有快速吸附性能。2、利用阴离子表面活性剂十二烷基苯磺酸钠(LAS)作为结构调控剂水热辅助制备了纳米多级结构MIL-100(Fe)([{Fe3O(H2O)2F0.81(OH)0.19}{C6H3(CO2)3}2]-nH2O(n=14.5)),考察了LAS的不同用量与纳米多级结构MIL-100(Fe)尺寸之间的关系。并运用PXRD、红外光谱(IR)和SEM对纳米多级结构MIL-100(Fe)结构、形貌和尺寸进行了表征。同时,考察了纳米多级结构MIL-100(Fe)与MIL-100(Fe)微晶对MB的光催化降解对比试验,试验结果表明纳米多级结构MIL-100(Fe)对MB的光催化降解效率较高,它可以用作新型光催化剂降解有机染料处理废水。3、以高分子聚乙烯醇(PVA)作为软模板,采用水热法制备了以铬为金属中心,以对苯二甲酸为有机配体的具有新颖形貌如：纳米颗粒、棒状等形貌和不同尺寸的MOFs材料。考察了不同PVA用量与MOFs形貌、尺寸之间的关系,并用PXRD和SEM等对其结构、形貌和尺寸进行表征。更多还原

【Abstract】 Recent ten years, MOFs as new class of porous crystalline materials built from metal ions building units connected by organic linkers have attracted much more attentions owing to their large pore sizes, high apparent surface areas, low density, tunable pore metrics, flexible tailoring, various topologies, and promising applications in hydrogen storage, adsorption, molecular recognization, sensing, catalysts, and drug delivery.However, most of the reported microporous MOFs display some restrictions because narrow pores do not allow accessing of bulky molecules to their internal surface, thereby limiting their practical applications in heterogeneous catalysis, absorption and separation. In contrast, meso-and macropore MOFs may meet the demands for the growing applications emerging in processes involving large molecules due to large pore volumes and high surface areas. According to the principle of molecular engineering, and crystal engineering, rational design and synthesis of meso-and macropore MOFs crystalline materials by selecting special metal ions and functional organic ligands remains a great challenge. In many cases the framework itself often breakdown upon removal of the guest molecules. At the same time, much more attention has turned to preparation of nano-scale hierarchical structured MOFs with meso-and macropore using surfactants as structure directing agents (SDA) to reduce the diffusion path length to fit the potential applications in sensing, molecule separation, and heterogeneous catalysts. The main contents of this thesis are as follows:1. Hierarchically mesostructured MIL-101metal-organic frameworks (MOFs) were successfully synthesized under solvothermal synthesis conditions by using the cationic surfactant cetyltrimethylammonium bromide as a supramolecular template. The mesostructured MIL-101MOFs were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms at77K. The results suggest that the mesostructured MIL-101MOFs obtained are composed of numerous MOF nanocrystals. Pore size distribution analyses of the as-synthesized MOF samples reveal that such mesostructured MIL-101MOFs have well-defined trimodal pore size distributions showing simultaneous existence of meso-and macropore channel systems. Significantly, such hierarchically mesostructured MIL-101exhibits remarkably accelerated adsorption kinetics for dye removal in comparison with the bulk MIL-101crystals, which is due to unique hierarchically meso-and macropores created in the solid.2. Successfully synthesized hierarchically structured MIL-100(Fe)nanocrystalline MOFs using anionic surfactant sodium dodecyl benzene sulfonate (LAS) as structure-directing agent under solvothermal conditions. The structures were confirmed by PXRD, infrared spectrum (IR), SEM, TEM, and nitrogen adsorption-desorption isotherms at77K. The results show that the hierarchically structured MIL-100(Fe) MOFs size of nanocrystals can be tuned by varying dosage of LAS. Significantly, such hierarchically structured MIL-100(Fe) nanocrystalline exhibits remarkably photocatalytic decolorization of methylene blue (MB) dye in comparison with the bulk MIL-100(Fe) crystals, which is due to unique hierarchically meso-and macropores created in the solid. This may be helpful to design novel photocatalyst materials.3. Novel morphologies of MIL-101(Cr) were successfully synthesized via a novel polymer polyethylene alcohol (PVA) surfactant-assisted technique. The characterized by PXRD, SEM, and nitrogen adsorption-desorption isotherms at77K. The results indicated that size and shape of can be tuned by varying of dosage of PVA. The pore size distribution date show that as-synthesized MOF samples existence of meso-and macropore channel systems.更多还原