Experiment : Synthesis of Isostructural Zr6-Based Metal-Organic Frameworks

Experiment 6:  Synthesis of Isostructural Zr6-Based Metal-Organic Frameworks

Experiment 6

Khoa Nguyen

40078865

Abstract:

Organic metal frame (MOF) is made up of more than two types of metal ions mixed in one secondary building. In fact, the metals of group 4 on the periodic table are commonly used to synthesize the MOFs. They are consider due to their superior chemical stability, and structural tunability. Therefore, they have strong tolerance to defects and the ability to adjust unlimitedly through disability techniques. In this experiment, we are going to isolate, dry and analyze samples of Zr6MOFs UiO-66 and UiO-67 by using powder Xray diffractions (PXRD).

Introduction:

In the past two decades, the research on a class of organic-inorganic hybrid material has been focused and developed in in synthesis and application. MOFs structure is linked by a coordination bond among inorganic nodes and organic linkers. In term of inorganic nodes, they can be metal cluster or metal ions, and carboxylates or heterocylic compounds plays as organic linekers. The design of organic linkers; specific lengths, geometries, and its functional group play an important role in the structure and fuction of MOFs, whereas, inorganic nodes municipalize some MoF properties. To illustrate, metal-ligand bonds are the most labile sites of the framework, and inorganic nodes determined the chemical stability of a MOFs. Literally, All metal cations, including some radioactive ones can be used to build up MOFs as inorganic nodes. They can be a monovalent, divalent, trivalent, and tetravalent metal cations. In the first stage of the research, Zn2+ and Cu2+ was used the most to build up MOFs. However, they are ultimately limited by their instability harsh condition. From that point, researchers have been working on finding new materials. As a result, a new stable framework structeres Zr-MOF, UiO-66 is introduced in 2008.(Stefan J, 2015) Ui0-66  is a metal organic framework made up of [Zr6O4(OH)4] clusters with 1,4-benzodicarboxylic acid struts. ( Zahra, 2018).  UiO-66 possesses two types of micropopers, tetrahedral, and octahedral. Beside that, there is an isotructure of UiO-66 which is called UiO-67. It contains 4,4 -biphenlldicarboxylic acid BPDC linker. (Habiba, 2017).

Results

Table 1. Experimental results

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Graph 1: Powder X-ray diffraction (PXRD) pattern of Zirconium(IV) Oxychloride Octahydrate (UiO-66)

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Graph 2: Powder X-ray diffraction (PXRD) pattern of Zirconium(IV) Oxychloride Octahydrate (UiO-67)

Questions

1. What is the difference between isostructural and isomorphous? According to the title of this experiment, UiO-66 and UiO-67 are isostructural, why? Are they also isomorphous? (3 marks)

Isostructural means that they have the same connectivity. UiO-66 and UiO-67 are isostructural because they have the same ligand linear dicarboxylic acid linking up. Isomorphous means that their shape is identical. UiO-66 and UiO-67 are isomorphous because they both are hexagonal and have the same size.

1. In relation to MOF chemistry, what is a modulator? Why do we use HCl as a modulator in this experiment? (3 marks)

A modulator slows the growth of the metal organic framework (MOF). HCl can decompose DM. It can break coordination bonds, and compete in order to bind to the ligand. Therefore, HCl con slow down the reaction.

1. What is solvothermal synthesis? (2 marks)]

A solvent at high temperature is used to dissolve material under high pressure and high temperature.

1. How are the powder X-ray diffraction patterns of UiO-66 and UiO-67 the same? How are they different? What do the similarities and differences in the patterns tell us? (2 marks)

As the ansewer above, UiO-66 and UiO-67 are isostructural, so their patterns of peaks are the same. However, there is only difference which is the peak of UiO-67 are longer due to (longer ligand), longer atomic distance thus lower angles which caused a shift. Overall, the x-ray patterns are the same but the length of those peaks is different.

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