钛氧簇合物与锆金属有机框架的合成与光催化性质研究

发布时间：2018-11-04 12:04

【摘要】：金属氧簇,即多金属氧酸盐,简称多酸,从首次合成报道到如今不过百年历史。它的应用研究已从最初的催化领域扩展到磁性领域、催化领域、手性与仿生领域、纳米材料与表面化学领域,由于近些年人类意识到能源日益枯竭,开发新的稳定清洁能源势在必行,因此科研工作者们把目光投向了多酸这一具有优秀催化性能的无机化合物。IIB族过渡金属中的钛与锆具有较低的能带间隙,十分适合做太阳能电池以及光催化剂,且对于钛的重要化合物二氧化钛作为太阳能产氢的光催化剂已研究的较为深入和广泛。相比于二氧化钛这种常规的光催化剂,钛氧簇合物与锆的金属有机框架结构具有更多的优势:可以与各类有机配体结合增加对光谱吸收的范围,使其可以应用太阳能中最大比例的可见光;形成的框架结构利于电子传输,使光解水产氢效率增加。目前对于钛氧簇的研究,在新结构合成方面已经到达平台期,科研工作者更注重对已知结构的光催化性质拓展,通过对其功能化、对结构优化以扩展其对光吸收范围,增加光催化产氢效率。而对于锆氧簇和锆金属有机框架的研究起步较晚,如今还处在初级阶段,其光催化产氢性质研究较少,这将是我们科研的重点方向之一。本文摒弃传统方法中合成钛氧簇的毒性较高溶剂,采用醇类在较低温条件下合成了三种六核钛氧簇:Ti6O4(OEt)4(OiPr)4[OOCC6H5]8(1),Ti6O4(OEt)8[OOC(CH3)3]8(2)和Ti6O4(OCH3)8[OOC(CH3)3]8(3)。三者的空间群均为P21/c,但由于配体不同,其空间结构略有不同。化合物2与3中[Ti6O4]在超过24小时加热100°C的条件下,会有分子部分进行原子重排,形成另一种紧凑的[Ti6O6]结构,分子式分别为Ti6O6(OEt)6[OOC(CH3)3]6与Ti6O6(OCH3)6[OOC(CH3)3]6,然而化合物1持续加热超过3天未出现Ti原子重排现象。对三种化合物及2与3重排产物的光催化性质进行研究,发现三种化合物的光催化产氢量与产氢效率均高于同样条件下所测得的纳米级二氧化钛,且2与3重排后并不影响催化性能。对于锆的金属有机框架结构合成与催化性质研究,我们还在进行中。
[Abstract]:Polyoxometalates, or polyoxometalates, have been synthesized for a hundred years since their first synthesis. Its applied research has expanded from the original catalysis to the magnetic field, the catalysis field, the chiral and bionic field, the nanomaterials and the surface chemistry field, because in recent years the mankind realizes the energy resources to be exhausted day by day. It is imperative to develop new and stable clean energy sources, so researchers have turned their attention to polyacid, an inorganic compound with excellent catalytic properties. Titanium and zirconium in IIB transition metals have low energy band gap. It is very suitable for solar cells and photocatalysts, and titanium dioxide, an important compound of titanium, has been studied deeply and extensively as photocatalyst for hydrogen production from solar energy. Compared with titanium dioxide, a conventional photocatalyst, titanium oxide cluster has more advantages than zirconium organometallic framework structure: it can be combined with various organic ligands to increase the range of spectral absorption. Make it possible to apply the largest proportion of visible light in the solar energy; The formed frame structure is favorable for electron transport and increases the efficiency of photodissociation of aquatic hydrogen. At present, the research on titanium oxide clusters has reached the plateau stage in the aspect of new structure synthesis. Researchers pay more attention to the development of photocatalytic properties of known structures, and optimize the structure to expand the range of light absorption by functionalizing it. Increase the efficiency of photocatalytic hydrogen production. However, the research on zirconium oxide clusters and zirconium organometallic frameworks started late, and are still in the primary stage, and the photocatalytic hydrogen production properties are less studied, which will be one of the key research directions of our research. In this paper, three kinds of hexanuclear titanium oxide clusters, Ti6O4 (OEt) 4 (OiPr) 4 [OOCC6H5] 8 (1), were synthesized by alcohols at lower temperature. Ti6O4 (OEt) 8 [OOC (CH3) 3] 8 (2) and Ti6O4 (OCH3) 8 [OOC (CH3) 3] 8 (3). The spatial groups of the three groups are all P21 / c, but their spatial structures are slightly different due to the different ligands. In compounds 2 and 3 [Ti6O4], when heated for more than 24 hours at 100 掳C, there will be an atomic rearrangement of the molecular parts to form another compact [Ti6O6] structure, The molecular formulas are Ti6O6 (OEt) 6 [OOC (CH3) 3] 6 and Ti6O6 (OCH3) 6 [OOC (CH3) 3] 6, respectively. However, no Ti rearrangement occurred in compound 1 for more than 3 days after continuous heating. The photocatalytic properties of the three compounds and the 2 and 3 rearrangement products were studied. It was found that the photocatalytic hydrogen production and hydrogen production efficiency of the three compounds were higher than those of nanometer titanium dioxide measured under the same conditions. After rearrangement of 2 and 3, the catalytic performance was not affected. We are still studying the structure synthesis and catalytic properties of zirconium.
【学位授予单位】：东北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O627;TQ116.2

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