Hexacoordinate Si/Ge compounds and their application in metal-organic frameworks
Author(s)
Tian, Shouyi
Type
Thesis or dissertation
Abstract
Metal-Organic Frameworks (MOFs) are porous coordination polymers comprising metal clusters linked by organic linkers, forming intricate framework structures. In recent decades, research on MOFs has gained attention due to their diverse structures and potential applications in gas storage/separation, catalysis, chemical sensing, and drug delivery. The organic connectors impart unique properties to these materials, make the synthesis of new connectors pivotal for exploring MOFs with novel structures and properties. Chapter 1 offers an overview of MOF chemistry, encompassing historical development, design and synthesis, activation, and characterization. The utilization of hexafluoro silicate/germanate anions (SiF62-/GeF62-) in MOF assemblies and their applications, and examples of COF/MOFs containing SiO6/GeO6 units are highlighted. Chapter 2 introduces hydrogen-bonded organic frameworks, and methodologies for synthesizing hexacoordinated Si/Ge connectors. Twenty-one anionic linkers featuring EO6 centres [E = Si or Ge, L1-Si/Ge: tris-oxalate silicate/germanate, L2-Si/Ge: tris(3-(3,4-diolatophenyl)acrylic acid) silicate/germanate, L3-Si/Ge: tris(3,4-diolato-benzoic acid) silicate/germanate] have been synthesized with different ammonium cations for charge balance, and characterized by NMR and IR spectroscopy and PXRD, and crystals of some compounds have been studied through SCXRD analysis. These structures exhibit H-bond interactions, with some self-assembling into extended networks. Chapter 3 introduces rare earth (RE) MOFs and their applications. Ten RE-MOFs were prepared by treating RE salts (Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) with [(Et3NH)2(L3-Ge)]. SCXRD studies revealed that the Y-MOF and all Ln-MOFs are isostructural, comprising bimetallic clusters, while Sc-MOF contains trimetallic clusters. Chapter 4 describes the luminescence mechanisms of f-block elements and applications of Tb-based MOFs. The photoluminescence properties of the Tb-MOF were studied, with characteristics emission under UV excitation. The sensing performance toward metal ions was investigated, showing significant quenching by Pb2+ ions with a quench efficiency of 1.80 × 103 M-1, involving a dynamic quench mechanism.
Version
Open Access
Date Issued
2024-06-13
Date Awarded
2024-09-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Davies, Robert
Lickiss, Paul
Publisher Department
Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)