武汉理工大学毕业设计（论文）

Construction of 1D Structures from
MOP Units

学院（系）： 材料科学与工程学院

专业班级： 材料科学与工程专业 1202班

学生姓名： 吴兆轩

指导教师： Francis Verpoort

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作者签名：

2016年05月15日

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作者签名： 2016年05月15日

导师签名： 2016年05月15日

Abstract

Despite tremendous efforts, precise control in the synthesis of porous materials with pre-designed pore properties for desired applications remains challenging. Newly emerged porous metal-organic materials such as metal-organic polyhedra and metal-organic frameworks are amenable to design and tuning, enabling precise control of functionality by accurate design at the molecular level. Here we successfully synthesized two kind new ligands, 3,3’-(Pyridine-2,6-diyl)dibenzoic acid (L2) and 3,3’-(Phenyl-1,3-diyl)dibenzoic acid (L3), which possess two carboxyl groups with 0 °C. Based on these two ligands, four innovative cubic MOPs were obtained under the confirmation of PXRD. Those two MOPs were constructed by two Cu paddlewheels at the top and bottom. Moreover, a precisely designed cavity is proposed and validated, termed a ‘single-molecule trap’, with the desired size and properties suitable for trapping target molecules. Such a single-molecule trap can strengthen CO₂–host interactions without evoking chemical bonding, thus showing potential for CO₂ capture. Molecular single-molecule traps in the form of metal-organic polyhedra are designed, synthesized and tested for selective adsorption of CO₂ over N₂ and CH₄, demonstrating the trapping effect. Building these pre-designed MOPs into extended chains yields metal-organic chains with efficient mass transfer, at the presence of pyrazine or bipyridine, whereas the CO₂ selective adsorption nature of single-molecule traps is preserved.

Keywords: metal organic polyhedral (MOP); metal organic chain; Suzuki coupling reaction; CO₂ selective adsorption;

Catalogue

Chapter 1. Introduction 1

1.1 Background and Significance of Metal Organic Polyhera 1

1.2 Background and Significance of Metal Organic Framework 3

1.3 Purpose and Novelty of the Proposed Research 6

1.4 Research Design and Methodology 6

Chapter 2. Experimental Parts 11

2.1 Materials and Methods 11

2.2 Preparation of Ligands 11

2.2.1 Synthesis of 3,3’-(Pyridine-2,6-diyl)dibenzoic acid, [H₂(3,3’-PDDB)] (L2) 11

2.2.2 Synthesis of 3,3’-(Phenyl-1,3-diyl)dibenzoic acid, [H₂(3,3’-PDDB)] (L3) 12

2.3 Preparation of MOPs and 1D Architectures 13

2.3.1 Synthesis of MOP-1-DMA [Cu₂(L²)₂(DMA)₂]₂ 13

2.3.2 Synthesis of MOP-2-DMA [Cu₂(L³)₂(DMA)₂]₂ 13

2.3.3 Synthesis of 2D constructions (Chain 1-3) from
MOP-1-DMA [Cu₂(L²)₂(DMA)₂]₂ 13

2.3.4 Synthesis of 2D constructions (Chain 4-6) from
MOP-2-DMA [Cu₂(L³)₂(DMA)₂]₂ 14

Chapter 3. Results and Discussion 15

3.1 Synthesis and Characterization of the ligand 2, 3 15

3.2 Analysis of PXRD Spectrum 16

3.3 Analysis of TGA-DSC Spectrum 21

3.4 Gas adsorption of MOPs and 2D constructions 28

Chapter 4. Conclusion 36

References 38

Acknowledgements 40

Chapter 1. Introduction

1.1 Background and Significance of Metal Organic Polyhera

Metal-organic polyhedra (MOPs) have attracted great interest in the past decade. The booming development of the supramolecular chemistry as a research field beyond the molecules, focused on the discrete chemical system made up of a discrete number of assembled molecular components or subunits. Dynamics of supramolecules, reveal that ligands and metal ions can construct self-assemblies due to non-covalent forces, including metal coordination, hydrogen bonding, hydrophobic forces, Van der Waals forces, electrostatic effects and etc.¹ Apparently, metal-organic polyhedral structures are regarded as three dimensional architectures, whereas there are exciting 1 or 2 dimensional materials,^2,3,4 metal organic polymers (1D)⁵ and metal organic polygons (2D)⁶. For instance, a large number of 2D systems (triangles, squares, rectangles and rhomboids, etc.) have been reported. The research for novel MOPs has driven the exploration of geometries, including tetrahedrons,^7,8,9 cubes,^10,11,12 octahedrons, ^12,13,14 cuboctahedrons,¹⁵ prisms,^16,17,18 rhombic dodecahedrons^19,20,21 and large spherical structures reminiscent of viral capsids,^22,23 due to the valuable efforts of Zhou,^10,24,25 Fujita,²⁶ Nitschke,²⁷ Raymond^28,29 and Yaghi ⁴ and co-workers.

A particularly synthetic method is utilized for the construction of MOPs by linking of building blocks known as secondary building units (SBUs) with a wide range of linkers, one popular kind of these SBUs is recognized as “paddlewheel” with formula M₂(-CO₂)₄ using dicarboxylic linkers. Through designing different types of SBUs based on topologies, lots of metal organic materials have been built and an increasing number of opportunities and challenges have been faced. Different from networks which are called metal organic frameworks (MOFs), a mature research area, which takes advantages of high surface area and applied in adsorption and separation of mixed gases,³⁰ MOPs in nano-size take much attention, which are also called nanoparticles, nanocages, nanoballs, nanospheres or nanocapsules. As a new series of nano-material, MOPs have high outer and inner specific surface areas, and are able to be applied in catalysis,^{31,32,29,33,34,35} gas sequestration,^36,10,37 photoreactions,^38,14,39 drug delivery,²⁶ molecule sensing⁴⁰ and stabilization of reactive species.^41,42,43

Prodigious developments in the material science reflect that humanity has travelled a great distance from the stone-age to the current modern-age. Right from the beginning, man is looking forward to engineer new materials to successfully deal with the challenges. Around the globe material scientists are actively engaged in exploring the high profile of featured properties and functional stability for the required value for various materials. Therefore, material science has become highly useful in designing the formulation and characterization of materials from very simple to symmetrically self-assembled molecular architectures and technological processes. In supramolecular science, self-assemblies with the highest degree of symmetry composed of multiple numbers of subunits are very common in biological systems.

Learning from these natural extremely symmetric biological self-assemblies, numerous artificial/abiological self-assembled polyhedra based on metal-organic constituents have been built. These polyhedral assemblies have been introduced as a new class of materials among other famous and well known metal organic materials.

Before the end of 20th century the concept of molecular nanosize containers was introduced and compounds constituted from different chemical formulations like organic or metal-organic were reported. Metal-organic polyhedra (MOPs), are not infinite networks like metal-organic frameworks (MOFs), but are discrete molecular entities constructed from the self-assembly of edge-sharing molecular polygons or from the connection of molecular vertices. MOPs are discrete at the size of nanoscale cage like architectures having an outer and inner surface and are also termed as nanocages, nanospheres, nanocapsules or nanoballs. MOPs have potential applications in material science by acting as host molecules that present tolerable in-house capacity described in the terms of functionality, metrics and active metal sites. Inspired from this aspect MOPs have become attractive for works in catalysis, drug delivery, gas sorption, acting as secondary building blocks for nanoporous coordination networks, molecular recognition and sensing, etc.