Abstract
Low- and zero-valent metals are of great interest, as their reducing nature enables chemical transformations restricted for their oxidized counterparts. This thesis entitled ”Expanding the Field of Zero- and Low-Valent Metals in Metal-Organic Frameworks” explores incorporating low- and zero-valent metals as metals nodes into polymeric structures such as metal-organic frameworks (MOFs). The main focus is on expanding current synthetic approaches to tether electron rich metals into porous frameworks, aiming at translating their unique properties into heterogeneous environments more applicable towards applications.
The first chapter is a guide to understanding the field of metal-organic frameworks and the underlining chemical principles behind their synthesis and applications. The general introduction is then followed by a brief introduction of how low-valent metals has been incorporated into existing MOF-scaffolds, as well as a discussion on their reactivity and applications. Finally, currently known zero-valent metal-organic frameworks are outlined and discussed.
In Chapter 2 the synthesis and properties of zero-valent metal-organic frameworks incorporating fac-M(CO)3(𝜇-diimine)3/2 (M = Cr, Mo, W) metal nodes is described and discussed. Reactions between M(CO)6 (M = Mo, W) and 4,4′-bipyridine (bpy) under harsh conditions leads to the formation of a 3D interpenetrated network with {fac-M(CO)3} moieties tethered in space by bpy ligands. The interactions of these frameworks with light, as well as their vapor phase synthesis is reported and discussed. A more porous network could be obtained by using the bulkier 3,3′-dimethyl-4,4′-bipyridine (dmBpy) linker, leading to 2D networks connected with fac-M(CO)3(𝜇-dmBpy)3/2 (M =Cr, Mo, W) units. These networks exhibit large pores with diameters above 1 nm, with permanent porosity confirmed by gas sorption experiments. The networks were synthesized with the use of fac-M(CO)3(pyridine)3 as a precursor, allowing for an exceptionally easy and fast synthesis with reaction times down to a few minutes, highlighting the use of precursors with kinetically labile ligands to obtain crystalline frameworks. The networks with Mo and W metal nodes phosphoresce with lifetimes on the nano- to micro-second scale, and their photophysical properties are comparable to known photoactive molecular analogues.
Chapter 3 describes synthetic efforts and strategies towards tethering zero-valent group 6 metal centers with isocyanide ligands, as well as the synthesis and characterization of the first zerovalent cluster-organic framework. The cluster, consisting of Pd3 nodes tethered in 2D with easily obtained isocyanide linkers, is characterized with a variety of techniques, and a focus is put on the EXAFS modeling performed to verify the connectivity of Pd in bulk samples.
Chapter 4 presents a new family of 1D fac-Re(CO)3X(𝜇-diimine)2/2 chains (X = Cl, Br). 4 different chains are obtained with three different diimines, and their structural and photophysical properties are compared to photoactive molecular analogues. Notably, fac-Re(CO)3X(𝜇-bpy)2/2 luminesce akin to that of the known CO2 reduction photocatalyst fac-Re(CO)3Cl(2,2′-bipyridine), though proof-of-concept photocatalysis does not show a significant catalytic ability.
Lastly, the main results of all chapters are summarized in ”Summary and Outlook”, and future routes for further development of the presented systems are suggested.
The first chapter is a guide to understanding the field of metal-organic frameworks and the underlining chemical principles behind their synthesis and applications. The general introduction is then followed by a brief introduction of how low-valent metals has been incorporated into existing MOF-scaffolds, as well as a discussion on their reactivity and applications. Finally, currently known zero-valent metal-organic frameworks are outlined and discussed.
In Chapter 2 the synthesis and properties of zero-valent metal-organic frameworks incorporating fac-M(CO)3(𝜇-diimine)3/2 (M = Cr, Mo, W) metal nodes is described and discussed. Reactions between M(CO)6 (M = Mo, W) and 4,4′-bipyridine (bpy) under harsh conditions leads to the formation of a 3D interpenetrated network with {fac-M(CO)3} moieties tethered in space by bpy ligands. The interactions of these frameworks with light, as well as their vapor phase synthesis is reported and discussed. A more porous network could be obtained by using the bulkier 3,3′-dimethyl-4,4′-bipyridine (dmBpy) linker, leading to 2D networks connected with fac-M(CO)3(𝜇-dmBpy)3/2 (M =Cr, Mo, W) units. These networks exhibit large pores with diameters above 1 nm, with permanent porosity confirmed by gas sorption experiments. The networks were synthesized with the use of fac-M(CO)3(pyridine)3 as a precursor, allowing for an exceptionally easy and fast synthesis with reaction times down to a few minutes, highlighting the use of precursors with kinetically labile ligands to obtain crystalline frameworks. The networks with Mo and W metal nodes phosphoresce with lifetimes on the nano- to micro-second scale, and their photophysical properties are comparable to known photoactive molecular analogues.
Chapter 3 describes synthetic efforts and strategies towards tethering zero-valent group 6 metal centers with isocyanide ligands, as well as the synthesis and characterization of the first zerovalent cluster-organic framework. The cluster, consisting of Pd3 nodes tethered in 2D with easily obtained isocyanide linkers, is characterized with a variety of techniques, and a focus is put on the EXAFS modeling performed to verify the connectivity of Pd in bulk samples.
Chapter 4 presents a new family of 1D fac-Re(CO)3X(𝜇-diimine)2/2 chains (X = Cl, Br). 4 different chains are obtained with three different diimines, and their structural and photophysical properties are compared to photoactive molecular analogues. Notably, fac-Re(CO)3X(𝜇-bpy)2/2 luminesce akin to that of the known CO2 reduction photocatalyst fac-Re(CO)3Cl(2,2′-bipyridine), though proof-of-concept photocatalysis does not show a significant catalytic ability.
Lastly, the main results of all chapters are summarized in ”Summary and Outlook”, and future routes for further development of the presented systems are suggested.
| Original language | English |
|---|
| Publisher | DTU Chemistry |
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| Number of pages | 264 |
| Publication status | Published - 2024 |
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