系列铋基金属有机框架材料的制备、表征及其光催化性能的研究

发布时间：2018-01-02 09:06

本文关键词：系列铋基金属有机框架材料的制备、表征及其光催化性能的研究　出处：《山东大学》2016年硕士论文　论文类型：学位论文

【摘要】：金属有机框架(Metal-Organic Frameworks, MOFs)材料是一类利用金属离子或者金属氧化物团簇与有机配体之间的配位键作用组装成的具有网状框架结构的多孔固体材料。近年来,MOFs材料由于其比表面积大,高孔隙度以及结构-功能的多样可调性等结构性质,在多个领域如气体储存、选择性吸附与分离、催化、发光材料以及药物载体等各方面具有很好的应用前景。其中,光催化能够将太阳能转换为电能、化学能,进而用来分解水产生可再生氢能,降解污染物,还原C02等,成为解决能源短缺及环境污染等问题的有效途径,因此MOFs材料在光催化领域的应用受到广泛关注。MOFs材料在光催化上有其独特的优势,主要表现在两个方面：(1)结构-功能的可调性；(2)大的孔隙度和排列有序的孔道结构。利用MOFs材料结构-功能的可调性,通过对金属位点和有机配体的改变或者修饰等手段,实现对材料光催化性能的调节。具体在光催化上,表现为调节材料光吸收范围；提高载流子分离效率；暴露的不饱和金属位点促进光催化反应。此外,MOFs材料具有大的孔隙度、比表面积以及排列有序的孔道结构,有利于一些客体分子的引入,使其能够直接与MOFs上的活性位点进行接触,缩短了电子传输距离,提高了载流子的传输效率,进而促进光催化反应的进行。迄今为止,已经发现一些MOFs材料具有高效的光催化性能,并且被分别应用在光催化降解污染物、光解水产氢以及还原C02等方面。但是这些光催化MOFs材料大多是基于Ti, Zr, Fe等过渡金属元素的,对其他金属基MOFs材料的光催化研究还很少,因此探究一些由主族金属或其他金属组成的光催化MOFs材料是很有必要的。铋系无机半导体表现出优异的光催化性能,成为光催化领域的一大研究热点。对铋系光催化材料的研究已成体系,而且我们课题组研究了一系列铋系光催化材料,如Bi2O3, BiOX (X=C1, Br, I), Bi2O2CO3, BiVO4, Bi2SiO5等,积累了丰富的实践和理论经验。同时铋系材料储量丰富,环境友好无毒,稳定性好,而且铋离子具有灵活多变的配位构型,有利于构建结构多样的MOFs。基于以上分析,我们推测铋基MOFs材料在光催化降解有机染料、光解水产氢、产氧等方面具有很好的应用。因此,在本论文中,我们开发了几种新型的铋基MOFs光催化材料,并研究了它们的光催化反应机理,具体内容分为五章：第一章首先介绍了MOFs材料的相关背景知识、合成方法以及主要应用领域。其次就MOFs材料在光催化领域的研究进展做了简单的概述,总结了MOFs材料在光催化上的优势以及主要的光催化机理理论。接着介绍了铋基MOFs材料在光催化领域的研究进展。最后阐述了本论文的选题意义、研究思路和主要内容。第二章主要包括MOF材料Bi-mna的制备以及光催化性能、机理的研究。利用简单的溶剂热方法制备了MOF材料Bi-mna的粉末,对其进行了XRD, TG/DTA等基本的表征,证明了样品的纯度,并对材料的结构特点进行简单介绍。通过测定光电流响应和交流阻抗谱,发现Bi-mna具有优异的光电化学性质。然后利用光降解有机物染料和光解水产氧能力来表征Bi-mna的光催化性能,结果显示Bi-mna能够在可见光照射下高效降解有机染料RhB和MB,并且在6h内持续不断分解水产生氧气,表现出了高效的光催化活性。通过对Bi-mna的能带结构和电子分布等进行理论计算,我们提出了一种新型的光催化机理理论,即配体到配体电子转移(LLCT)过程,并用实验验证了这一理论。LLCT过程的发生,能够延长材料中光生载流子的寿命,从而促进光生载流子的有效分离,提高材料的光催化效率。在第三章中,我们选用有机配体均苯三酸(H3BTC),制备两种铋基MOFs材料并对其光物理和光催化性能进行研究。(1)首先合成了一种新型铋基MOF材料Bi-BTC的单晶,并通过X射线单晶衍射技术得到了Bi-BTC的晶体结构信息。Bi-BTC中具有二聚体{Bi2014｝,这些{Bi2014｝基团之间由配体BTC3-连接形成了三维的框架结构。同时,沿b轴方向,{Bi2014｝基团通过配体的连接分别形成两种不同的螺旋链,这两种螺旋链交替排列,相邻的螺旋链共享一组{Bi2014｝二聚体,以一定的夹角组装在一起。漫反射光谱研究结果表明Bi-BTC的光吸收主要由配体引起,同时配体与铋的键合使其配位环境改变,引起了漫反射光谱和荧光发射光谱中的红移现象。初步研究发现,Bi-BTC具有在全光照射下分解水产生氧气的光催化活性。(2)我们在尝试合成Bi-BTC单晶的过程中,获得了Bi-BTC的一种同素异构体BiO-BTC。BiO-BTC是以甲酸氧铋(BiOHCOO)和H3BTC作为原料进行溶剂热反应获得的。根据BiOHCOO的离子交换性质我们推测这种材料是一种层状的有机无机杂化材料,由BTC阴离子替代BiOHCOO中HCOO-层获得的。通过对材料进行EXAFS,XRD,FT-IR以及热分析等测试对以上推测进行了验证。BTC阴离子的引入并没有改变原来的层状结构,仅仅使Bi2022+层发生结构的扭曲。研究其光催化活性,发现这种材料在全光下的光催化降解RhB活性相对于BiOHCOO有明显的提高,还有一定的光解水产氧活性。我们推测由于BTC阴离子的引入,引起Bi2022+层发生结构的扭曲,影响了电子转移过程,从而提高了光生载流子的存活寿命,提高了材料光催化活性。第四章主要是对基于其他有机配体的铋基MOFs材料的制备以及光催化等性质进行探究。首先制备了一种基于3,5-吡啶二羧酸(3,5-H2PYDC)的MOFBi-PYDC,并对其结构进行了介绍。通过探究Bi-PYDC的光催化性能,发现其在全光照射下能够降解RhB染料分子。此外,还发现Bi-PYDC具有离子交换的性质,与有机配体H3BTC进行离子交换,能够得到上章提到的有机无机杂化材料BiO-BTC。之后,我们选用2-氨基对苯二甲酸(NH2-H2BDC)为有机配体,借鉴第三章中的离子交换方法,得到有机无机杂化材料BiO-BDC(NH2)。通过对其光物理和光催化性能的研究,发现BiO-BDC(NH2)具有可见光响应,而且能够在可见光照射下高效的降解有机染料RhB,具有良好的光催化活性。第五章为总结与展望。我们主要是对论文中的工作和得出的理论进行了总结,列出了论文的创新点,并提出了工作中存在的问题和不足,以及未来工作的计划。总体来说,通过本论文对一系列铋基MOFs材料的研究及其光催化性能、机理的探究,充分说明铋基MOFs材料对于光催化领域具有重要意义,可发展为一种新型的光催化材料体系。
[Abstract]:Metal organic frameworks (Metal-Organic, Frameworks, MOFs) material is a porous solid materials with mesh frame structure between a class of using metal ions or metal oxide clusters and organic ligand bond assembled. In recent years, the MOFs materials due to its large surface area, high porosity and structural functional diversity adjustability the structure properties in many fields such as gas storage, selective adsorption and separation, catalysis, and has good application prospects in all aspects of luminescent materials and drug carriers. Among them, the photocatalytic conversion to solar energy into electrical energy, chemical energy, and then used to decompose water to produce renewable hydrogen energy, degradation of pollutants, such as reduction of C02 that is an effective way to solve the energy shortage and environmental pollution problems, so the application of MOFs material in the field of photocatalysis has attracted wide attention in the photocatalytic material.MOFs has its unique The advantages, mainly in two aspects: (1) the structure and function of the adjustable; (2) the porosity and pore structure ordered by MOFs material. The structure function is obtained, based on the metal sites and organic ligands change or modification and other means to achieve the regulation of photocatalytic properties specific in photocatalysis, appears to regulate the material light absorption range; improve carrier separation efficiency; exposure of unsaturated metal sites to promote the photocatalytic reaction. In addition, the MOFs material has high porosity, specific surface area and Kong Daojie ordered the introduction to some guest molecules, which can directly contact with the active site of MOFs, shorten the electronic transmission distance, improve the transmission efficiency of the carrier, and then promote the photocatalytic reaction. So far, MOFs has found some material with high light. The performance, and are respectively applied in photocatalytic degradation of pollutants, photocatalytic hydrogen and the reduction of C02 and so on. But these MOFs photocatalytic materials are mostly based on Ti, Zr, Fe and other transition metal elements, on the photocatalytic studies of other metal based MOFs material is very few, therefore some inquiry is composed of a main group metal or other metal MOFs photocatalytic material is very necessary. Bismuth inorganic semiconductors exhibit excellent photocatalytic properties, has become a hot topic in the field of photocatalysis. Research on bismuth based photocatalytic materials has become a system, and our research group studied a series of bismuth based photocatalytic materials, such as Bi2O3. BiOX (X=C1, Br, I), Bi2O2CO3, BiVO4, Bi2SiO5 etc., has accumulated rich experience on theory and practice. At the same time, bismuth material is abundant, environmentally friendly non-toxic, good stability, and bismuth ion has flexible configuration, there are To construct a variety of MOFs. based on the above analysis, we speculate that the bismuth based MOFs material in the photocatalytic degradation of organic dye, photolysis of hydrogen, has good application for oxygen production and so on. Therefore, in this thesis, we developed a bismuth based MOFs photocatalytic materials of several novel, the photocatalytic reaction mechanism of their and study, the specific content is divided into five chapters: the first chapter introduces the related background knowledge of MOFs materials, synthesis methods and main application fields. Then MOFs materials research progress in the field of photocatalysis were summarized briefly, summarizes the advantages of MOFs materials in photocatalysis and photocatalytic mechanism of the main theory. Then introduced the research progress of bismuth based MOFs materials in the field of photocatalysis. Finally, this paper expounds the significance of the topic, research ideas and main content. The second chapter mainly includes MOF material Bi-mna preparation and photocatalysis The performance and mechanism research. MOF material Bi-mna powder prepared by a simple solvothermal method, has carried on the characterization of XRD, basic TG/DTA, proved that the purity of the samples, and the structural characteristics of the materials are briefly introduced. By measuring the photocurrent response and AC impedance spectroscopy, Bi-mna has found photoelectrochemical properties of excellent photocatalytic performance. Then the light degradation of organic dyes and photocatalytic oxygen ability to characterize Bi-mna, the results showed that Bi-mna under visible light irradiation, the degradation of organic dye RhB and MB, and continuously decompose water to produce oxygen in 6h, showed a high photocatalytic activity. Based on the band structure of Bi-mna and the electron distribution of the theoretical calculation, we propose a novel photocatalytic mechanism theory, namely the ligand to ligand charge transfer (LLCT) process, and verified this theory by experiment On the.LLCT process, can prolong the lifetime of photocarriers materials, so as to promote the effective separation of the photogenerated carriers and improve the photocatalytic efficiency of the material. In the third chapter, we use the organic ligand trimesic acid (H3BTC), the preparation of two bismuth based MOFs material and Study on its physical and light photocatalytic performance. (1) firstly synthesized a novel single crystal bismuth based MOF material Bi-BTC, and through X ray diffraction technique was obtained with two dimers {Bi2014} crystal structure information.Bi-BTC Bi-BTC, {Bi2014} between these groups by ligand BTC3- connected to form a 3D frame structure. At the same time, along with B the direction of the axis of {Bi2014} groups respectively form two helical chains through different ligands connect the two helical chains are arranged alternately, adjacent helical chains share a set of {Bi2014} two dimers, with a certain angle of diffuse reflection light are assembled together. The results show that the spectrum of the light absorption of Bi-BTC is mainly composed of ligand-induced, while ligand with bismuth bonding to the coordination environment change caused by diffuse reflection spectra and fluorescence emission spectra red shift. The preliminary study found that Bi-BTC has photocatalytic activity in optical irradiation decomposition of water to produce oxygen (2) process. We attempt to synthesize Bi-BTC single crystals, obtained a BiO-BTC.BiO-BTC Bi-BTC isomer is formic acid bismuth oxide (BiOHCOO) and H3BTC as raw materials obtained by solvothermal reaction. According to the BiOHCOO ion exchange properties we speculate this material is a kind of layered organic-inorganic hybrid materials by BTC anion substitution HCOO- layer BiOHCOO. Through EXAFS, the material of XRD, FT-IR and thermal analysis test of the above conjecture to introduce verification.BTC anion does not change the original lamellar structure only. Only the Bi2022+ layer structure distortion. Study on its photocatalytic activity, found that the photocatalytic degradation of RhB activity of this material in full sunlight compared to BiOHCOO has increased significantly, and the photocatalytic activity. We speculate that the oxygen anion caused by introducing BTC, Bi2022+ layer structure distortion, the effect of electron transfer. In order to improve the photocarrier lifetime of material is improved photocatalytic activity. The fourth chapter is to explore the preparation and photocatalytic properties of bismuth based MOFs materials of other organic ligands. The system is based on the first prepared a two 3,5- pyridine carboxylic acid (3,5-H2PYDC) based on MOFBi-PYDC, and the structure of introduced in this paper. The photocatalytic performance of Bi-PYDC, can be found in all optical irradiation degradation of RhB dye molecules. In addition, also found that Bi-PYDC has the property of ion exchange, and organic ligand H3 BTC ion exchange, then can get the chapter on organic inorganic hybrid material BiO-BTC. mentioned above, we selected the 2- amino acid (NH2-H2BDC) as organic ligand model in Chapter third ion exchange method, obtained the organic inorganic hybrid materials BiO-BDC (NH2). Through the study on the photophysical and photocatalytic properties, found BiO-BDC (NH2) with visible light response and RhB efficient degradation of organic dyes under visible light irradiation, with good photocatalytic activity. The fifth chapter is the summary and outlook. We mainly summarizes the thesis work and the theory, list the innovation of the paper, and put forward the existing in the work the problems and deficiencies, and plans for future work. In general, the research and the light of a series of bismuth based MOFs composite catalytic performance and mechanism of the inquiry, full description of bismuth based MOFs materials It is of great significance for the field of photocatalysis and can be developed into a new type of photocatalytic material system.

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

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