Selective gas sorption studies in metal-organic frameworks

Brown, Martyn Stewart (2016) Selective gas sorption studies in metal-organic frameworks. PhD thesis, University of Nottingham.

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Abstract

This thesis describes the synthesis and characterisation of several new metal-organic frameworks (MOFs). These frameworks have subsequently been used in gas sorption experiments to determine the selective adsorption of various guests.

Chapter 1

An introduction to MOFs and the current research, including a description of the synthesis and characterisation process, various applications and some known MOFs from the literature. A general experimental techniques section is included describing the various techniques used in this research.

Chapter 2

A series of isostructural Cu(II) frameworks, NOTT-150 – 153, have been synthesised containing different functional groups. The four functional groups (CH3, NH2, OH and COOH) have been chosen to investigate how they affect the selective adsorption of CO2 over other gases. The polarity of the functional groups is a key factor as the protons can form hydrogen bonds to guest molecules in the framework. The lone electron pairs on some of the functional groups also contribute to the selective adsorption of CO2 by binding to the C atom to form a T-shaped interaction. The selectivity of CO2 adsorption has been studied against CH4 and N2 at 298 and 273 K, with a specific focus on how each group binds to individual CO2 molecules, and the strength of these interactions, to determine the best functional group for CO2 selectivity.

Chapter 3

Group II MOFs are rare in the literature due to their tendency to form dense 2D layered structures. A series of 3D MOFs containing Group II metal ions that feature 1D porous channels have been synthesised. NOTT-408(Ca) and NOTT-410(Ba) were synthesised with a tolyl-2,4,6-tribenzoate linker, and are stable to desolvation and exhibit permanent porosity upon activation. The porous frameworks are utilised in gas sorption experiments to determine which metal centre, Ca(II) or Ba(II), has the propensity for greater selective adsorption of CO2. Gas sorption experiments were performed at 298 and 273 K over a pressure range of 0 – 1 bar to determine the selective adsorption of CO2 over CH4 and N2; and both frameworks were compared to the selectivity exhibited in a Mg(II) MOF, Mg-MOF-74.

Chapter 4

The MOFs synthesised in Chapters 2 and 3 were used to determine the selective adsorption of C2-hydrocarbons over CH4. The NOTT-150 – 153 series of frameworks have shown a small increase in selectivity depending on the choice of functional group. The lone electron pairs on the NH2 and OH functional groups interact with unsaturated C2-hydrocarbons, increasing their selective adsorption. The COOH functional group partially fills Cage A within the structure making diffusion through the pores more difficult for larger molecules. This is best shown in the selective adsorption of C2H2 vs CH4 which is significantly higher in NOTT-153 (191.9 at zero loading and 298 K), than in the other frameworks. NOTT-408(Ca) and 410(Ba) have shown good selectivity for the C2-hydrocarbons due to the narrow pore channels within the frameworks.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Schroder, Martin
Subjects: Q Science > QD Chemistry > QD241 Organic chemistry
Faculties/Schools: UK Campuses > Faculty of Science > School of Chemistry
Item ID: 31978
Depositing User: Brown, Martyn
Date Deposited: 22 Jul 2016 12:58
Last Modified: 24 Sep 2016 08:44
URI: http://eprints.nottingham.ac.uk/id/eprint/31978

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