Multifunctional polycarboxylic acid linkers for metal-organic frameworks assembly
File(s)
Author(s)
Mubarik, Nudrat
Type
Thesis
Abstract
The chemistry of metal-organic frameworks (MOFs) has grown over the past decade to now be a major research topic in modern interdisciplinary scientific research. MOFs are versatile ultra porous functional materials made of inorganic metal nodes and organic linkers. The MOFs can be decorated with desired functionalities by either using functionalized linkers for the synthesis or functionalities can be installed after the MOF synthesis. Combined approaches using both techniques together have also been reported. Chapter 1 presents an introduction to the historical developments in MOF chemistry, traditional synthesis strategies and the role of linker design in MOF synthesis. The various pathways to incorporate multiple functionalities into MOFs and the potential applications of MOFs are also highlighted. Chapter 2 is focused on the synthetic approaches used to design silane-based polycarboxylic acid linkers containing amide functionalities. Eight novel amide-extended carboxylic acid linkers have been synthesized including tetra, tri and bipodal linkers (L1, L2, L3, L6) and containing one amide group and one carboxylic acid group per linker arm. L4 is a monocarboxylic acid tetrapodal linker consisting of two amide groups per linker arm. Hence L4 is capable of forming similar structural topologies to L1 but possesses a longer linker arm length. L5 and L7 are tetratopic linkers consisting of one amide and two carboxylic acid groups per arm, whilst L8 is an octatopic linker. All synthesized linkers were fully characterised by 1H-NMR, 13C-NMR and 29Si-NMR, IR, and mass spectroscopy. Chapter 3 explores the use of these amide decorated silane based polycarboxylic acid linkers to prepare novel MOFs. The crystal structures of L1, L4 and L8 were discussed in this chapter which revealed that these linkers also have potential to form self-assembled hydrogen-bonded organic frameworks due to the presence of intermolecular hydrogen-bonded interactions and ᴫ-ᴫ stacking. L1 and L4 are shown to exhibit 2D network hydrogen bonded organic framework structures. Two novel 3D MOFs were synthesized using L1, namely MOF-1(Cu) and MOF-2(Co). The 3D framework structure of MOF-1(Cu) consisted of Cu-paddle wheel nodes and tetrahedral Si linkers arranged in the alternate layers. The 4-fold interpenetrated MOF structure exhibited pts topology, which was same as IMP-9 constructed from same Cu salt and TCPS linker. MOF-2(Co) possessed 3D framework structure consisted of Co nodes and L1 as struts. The Co nodes comprised of two Co atoms each exhibiting octahedral geometry, integrated into the extended framework structure with L1 struts to form a complex interpenetrated structure. Chapter 4 details a combinatorial approach used for the synthesis of UiO-66-R (where R = H, SO3Na, NH2) MOFs using a mixed linker approach. All synthesized MOFs were characterized by 1H-NMR and PXRD and it was found that increasing the percentage of BDC-SO3Na (monosodium 2-sulfoterephtahlic acid) linker decreased the measured surface area and crystallinity of the resultant MOF. The stability of UiO-66-R MOFs was studied in water, basic and acidic conditions and the structures were unchanged after 24 hours exposure as confirmed by PXRD patterns. UiO-66-SO3Na-15 was subjected to post-synthetic modification to incorporate organic cations (NEt4+). The CO2 uptake studies revealed a remarkable increase (9 wt% to 22 wt% at 1 bar, 298 K) in the post-synthetically modified UiO-66-SO3NEt4-15.
Version
Open Access
Date Issued
2023-03-13
Date Awarded
01/07/2023
License URL
Advisor
Davies, Robert
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)