基于Keggin型多金属氧酸盐的新型杂化材料设计和性能

发布时间：2018-05-15 19:05

本文选题：催化 + 质子传导　；参考：《东北师范大学》2017年博士论文

【摘要】：Keggin型多金属氧酸盐(POMs)是经典的多酸结构之一,也是最稳定、最容易合成、应用范围最广及目前研究的最深入的多酸类型。本文基于Keggin型多酸的结构特点及性能优势,设计合成了系列多酸基杂化材料,系统研究了它们的催化和质子传导性能。取得的主要创新性成果如下:1、制备了担载Keggin型H_5PV_2Mo_(10)O_(40)的金属有机框架(NENU-9),实现了杂化材料的纳米化,在燃油深度脱硫反应中展示了优异性能。Keggin型H_5PV_2Mo_(10)O_(40)是为数不多的能够以氧气为氧化剂实现石油深度脱硫的催化剂之一,但问题是如何将极性的多酸引入到油相。我们采用简单的常规溶液合成和机械研磨法,将H_5PV_2Mo_(10)O_(40)担载到多孔MOF中得到纳米化的杂化材料[Cu2(BTC)4/3(H2O)2]6[H_5PV_2Mo_(10)O_(40)](NENU-9N,BTC=均苯三甲酸)。BTC中的非极性苯环为多酸构筑了一个疏水的外表面,并在孔中形成输水的微环境,能够吸附芳香族硫化物起到预浓缩作用,并限制了反应底物与催化中心间距离,催化活性充分发挥。亚微米的NENU-9N催化剂粒子能够均匀、稳定地分散在模拟和真实柴油环境中,在以氧气为氧化剂的条件下,实现了对芳香族硫化物二苯并噻吩(DBT)的100%催化转化。本工作开辟了将极性多酸引入油相的新方法,实现了多酸催化剂在非极性溶剂中的固载、分散、分离、回收和再利用。简便、快捷的纳米晶制备方法为实现工业化生产提供了可能。2、实现了亚微米尺度多酸基MOF材料(NENU-3)的晶面调控,突破了传统多酸基多孔MOF催化材料的孔道尺寸限制效应。MOF作为催化剂常受其微孔特性的限制导致大尺寸反应底物无法进入催化剂孔内而催化活性大大降低。我们利用配位调节法实现了对多酸基MOF材料的形貌调控,通过加入与主体框架中的有机配体BTC结构类似的对甲基苯甲酸(pTA)作为配位调节剂,NENU-3的形貌从完全暴露{111}晶面的八面体逐渐过渡到完全暴露{100}晶面的立方体。由于在{111}晶面上裸露的多酸催化活性位点比{100}晶面上更多,对于无法进入催化剂孔道内部的大尺寸反应底物,立方体形貌的NENU-3比八面体形貌显示了更高的催化活性。该实验结果打破了传统多酸基多孔MOF催化材料的孔道尺寸效应,首次证实了在MOF催化剂中存在晶面效应。应用到生物柴油制备反应中,发现立方体形貌的NENU-3催化剂对长链脂肪酸(C12-C22)的转化率可达90%,是八面体形貌催化剂的4倍以上。3、在多酸基多孔MOF的三维孔道内构筑了连续、稳定的氢键网络,获得了在三正交方向具有一致质子传输路径的高性能质子传导材料。多酸是一类优秀的固态质子传导电解质。部分Keggin型多酸的质子电导率高达0.1S·cm-1以上。但是,多酸极易溶解于水等极性溶剂,而且在受热时(超过90℃)结晶水易失去,导致氢键网络破坏、质子传导路径被切断而失去导电性能。所以,如何构筑连续有序的氢键网络,提高固态多酸晶格中水的稳定性,增强保水性能,是多酸用作固体质子导电材料实际应用面临的问题。我们将给出质子能力极强的Keggin多酸H3PW12O40(HPW)和异烟酸(Ina)作为质子给体和氢键受体,引入到具有高对称结构的金属有机框架(HKUST-1)中,HPW和Ina交替固载在MOF的孔道中建立了在三正交方向上一致且连续的三维质子传输通路,克服了传统MOF质子导体中低维质子通路导致的电导率各向异性。同时,HPW的引入,改善了杂化材料的亲水性和保水性,在较低相对湿度(70%RH)下即可获得1.81×10-3 S cm-1的质子电导率,比母体框架提升了5个数量级。4、合成了具有高稳定性的多酸-氧化石墨烯(GO)杂化块体材料,解决了GO用作质子传导材料性能快速衰减及成膜后质子传输方向与氢键网络方向不一致的问题。以乙二胺为交联剂、引入HPW,设计合成了具有三维多孔结构的海绵状HPW-GO块体杂化材料。质子化的乙二胺共价连接到GO表面,与多酸阴离子具有强的静电作用,加之广泛的氢键作用,使多酸稳定的固载到有机胺修饰的GO杂化材料中。由于多酸引入到石墨烯片层间,材料的亲水性能得到了明显提高,同时由于氧化石墨烯片层上亚稳态的环氧基团被乙二胺还原并氨基化,提供了更加稳定的质子传输位点。该材料在60%的低相对湿度下展示出了高达1.02×10-2 S cm-1的质子电导率。并且连续工作一个月没有发生明显的性能下降。这种优秀的性能可以归因于三维的质子传输通路、丰富的质子跳跃位点以及块体结构消除了晶界电阻。5、制备了对阳离子有机染料具有高吸附性能的多酸功能化GO杂化材料,实现了在可见光作用下吸附材料的光再生,克服了传统多酸光催化剂由于静电作用对阳离子染料吸引而无法实现光降解的问题。将具有光催化活性的Keggin型多酸K4H3PTi2W10O40引入到多孔的胺功能化氧化石墨烯(FGO)中,构筑了多酸-二元胺-氧化石墨烯的多元杂化体系。由于在POM、FGO及染料间存在疏水-疏水、π-π相互作用以及静电吸引的协同作用,POMs-FGO杂化材料对阳离子染料亚甲基蓝(MB)和罗丹明B(RhB)均展示出了优秀的吸附能力,吸附量分别达到1095 mg/g和540 mg/g。通过线性电势扫描确定了FGO的带隙。由于胺化使石墨烯杂化材料价带中的部分O2p被N2p取代,缩小了杂化材料的带隙,实现了可见光吸收。同时多酸的引入对光生电子的捕捉和转移促进了电子-空穴对的分离,实现了杂化材料在模拟和真实太阳光照射下对吸附染料分子的光降解,吸附性能完全再生,且多次重复使用性能无明显降低。与传统的多酸基光催化剂不同的是,由于多酸和FGO纳米层对染料分子的竞争吸附效应,染料分子在多酸和FGO间形成了动态的吸附-脱附平衡,从而避免了对多酸表面的完全覆盖。该项研究打破了传统多酸光催化剂对阳离子染料光降解活性低的限制,为多酸基光催化材料的设计提供了借鉴。
[Abstract]:Keggin type polyoxometalate (POMs) is one of the classic polyacid structures. It is also the most stable, most easy to synthesize, the most widely used and the most widely studied polyacid type. Based on the structural characteristics and performance advantages of Keggin polyacid, a series of polyacid base hybrid materials are designed and synthesized. Their catalysis and protons are systematically studied. The main innovative results are as follows: 1, a metal organic frame (NENU-9) loaded with Keggin type H_5PV_2Mo_ (10) O_ (40) was prepared, and the hybrid material was nanoscaled. The excellent performance of.Keggin H_5PV_2Mo_ (10) O_ (40) was demonstrated in the deep desulfurization reaction of fuel oil, and the few were able to realize petroleum with oxygen as oxidant. One of the catalysts for deep desulphurization, but the problem is how to introduce the polar polyacid into the oil phase. We use a simple conventional solution synthesis and mechanical grinding method to carry H_5PV_2Mo_ (10) O_ (40) to the porous MOF to obtain the nanocrystalline hybrid [Cu2 (BTC) 4/3 (H2O) 2]6 [H_5PV_2Mo_ (10) O_ (40)] (NENU-9N, BTC=) three formic acid) The polar benzene ring forms a hydrophobic outer surface and forms a micro environment in which the water transport is formed in the hole. It can preconcentrate the aromatic sulfide and limit the distance between the reaction substrate and the catalytic center, and the catalytic activity is fully exerted. The sub micron NENU-9N catalyst particles can be evenly distributed in the simulation and the reality. In diesel environment, a 100% catalytic conversion of aromatic sulfide two benzo thiophene (DBT) was realized under the condition of oxygen as oxidant. This work opened up a new method of introducing polar polyacid into oil phase, and realized the immobilization, dispersion, separation, recovery and reuse of the polyacid catalyst in the nonpolar solvent. The preparation method provides the possible.2 for industrial production, realizes the crystal surface regulation of the submicron scale polyacid based MOF material (NENU-3), breaks through the pore size limitation effect of the traditional polyacid base porous MOF catalytic material,.MOF as the catalyst, which is often limited by the microporous properties of the catalyst, resulting in the failure of the large size reaction substrate to enter the catalyst hole. The morphology of the polyacid MOF material was regulated by the coordination method. By adding pTA as a coordination regulator with the structure of organic ligand BTC in the main frame, the morphology of NENU-3 was gradually transferred from eight sides of the {111} surface completely exposed to the {100} crystal surface. The cube. As the polyacid catalyzed active site exposed on the {111} surface is more than the {100} surface, the NENU-3 of the cube morphology shows higher catalytic activity than the eight surface morphology for the large size reaction substrate that can not enter the catalyst channel. The experimental results broke the traditional polyacid base porous MOF catalytic material Kong Daochi. It is first confirmed that there is a crystal surface effect in the MOF catalyst. In the preparation of the biodiesel, the conversion of the cubic NENU-3 catalyst to the long chain fatty acid (C12-C22) can reach 90%, which is more than 4 times the.3 of the eight surface catalyst, and the continuous and stable hydrogen is constructed in the three-dimensional porous MOF of the polyacid base porous MOF. Bond networks have obtained high performance proton conduction materials with uniform proton transmission paths in the three orthogonal direction. Polyacid is an excellent solid proton conduction electrolyte. The proton conductivity of partial Keggin polyacids is up to 0.1S. Cm-1. However, polyacid is easily dissolved in water and other polar solvents, and at the time of heating (over 90 degrees C) crystal water When the hydrogen bond network is destroyed easily, the proton conduction path is cut off and the conductivity is lost. Therefore, how to build a continuous and orderly hydrogen bond network to improve the stability of water in the solid polyacid lattice and enhance the water retention property is a practical problem for the use of polyacid as a solid proton conducting material. We will give a Keg with a very strong proton capacity. Gin polyacid H3PW12O40 (HPW) and isonicotinic acid (Ina), as proton donor and hydrogen bond receptor, are introduced into a highly symmetric structure of metal organic framework (HKUST-1). HPW and Ina are sequestrated in the channel of MOF to establish a consistent and continuous three dimensional proton transmission path in the three orthogonal direction, which overcomes the low dimensional proton conduction in the traditional MOF proton conductors. The conductivity is anisotropic. At the same time, the introduction of HPW improves the hydrophilicity and water retention of the hybrid material. The proton conductivity of 1.81 x 10-3 S cm-1 can be obtained under the low relative humidity (70%RH), and 5 orders of magnitude.4 are raised over the mother frame, and the high stability of the polyacid and graphene oxide (GO) hybrid block material with high stability is synthesized. GO is used as a problem for the rapid attenuation of proton conduction materials and the disagreement between the transmission direction of proton and the direction of the hydrogen bond network. Using ethylene diamine as a crosslinker, a sponge like HPW-GO block hybrid material with three-dimensional porous structure is designed and synthesized. The protonated ethamine is covalently connected to the GO surface and with the polyanic anions. With strong electrostatic action and a wide range of hydrogen bonding, polyacid is immobilized steadily into the GO hybrid material modified by organic amine. The hydrophilic property of the material has been greatly improved because of the introduction of polyacid to the graphene sheet. At the same time, the cyclic oxygen group of the metastable oxide on the graphite oxide layer is reduced and aminated by ethylenediamine. A stable proton transfer site was added. The material showed a proton conductivity up to 1.02 x 10-2 S cm-1 at 60% low relative humidity. And there was no apparent decrease in performance for a month for a month. This excellent performance can be attributed to a three dimensional proton transfer pathway, a rich proton jumping site and a block structure elimination. With the grain boundary resistance.5, a polyacid functional GO hybrid material with high adsorption properties to the cationic organic dyes was prepared. The optical regeneration of the adsorbed material under visible light was realized, and the problem that the traditional polyacid photocatalyst could not be degraded by the electrostatic action on the cationic dye was overcome. The photocatalytic activity of Keg was obtained. Gin polyacid K4H3PTi2W10O40 was introduced into the porous amine functionalized graphene oxide (FGO), and a polyacid - two - amine - graphene oxide hybrid system was constructed. There were hydrophobic, hydrophobic, pi - pi interaction and electrostatic attraction synergism between POM, FGO and dye, and POMs-FGO hybrid material to the cationic dye methylene blue (MB). Luo Danming B (RhB) showed excellent adsorption capacity, and the adsorption capacity reached 1095 mg/g and 540 mg/g. respectively to determine the band gap of FGO by linear potential scanning. Because amination made part of O2p in the valence band of the graphene hybrid material to be replaced by N2p, the band gap of the hybrid material was reduced and the visible light absorption was realized. At the same time, polyacid was introduced to photoelectricity. The separation of electron hole pairs is promoted by the capture and transfer of the subsurface, and the photodegradation of the adsorbed dye molecules in the hybrid materials under simulated and real solar irradiation is realized. The adsorption property is completely regenerated and the performance of repeated reuse has no obvious reduction. Unlike the traditional polyacid based photocatalyst, the dye is treated with polyacid and FGO nanoscale. The dynamic adsorption desorption equilibrium between polyacid and FGO is formed by the molecule's competitive adsorption effect, which avoids the complete coverage of the polyacid surface. This study breaks the limitation of the low photocatalytic degradation activity of the traditional polyacid photocatalyst and provides a reference for the design of the polyacid based photocatalytic material.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TE624.9

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