Metal-organic frameworks for water treatment

  • Qiang Wei

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract


This thesis investigates the application of metal-organic frameworks in waste water treatment and the synthesis of new metal-organic frameworks.

Chapter one gives a general overview of water-treatment processes, the methods and materials used in these processes, and also the structures and properties characteristics of activated carbon and zeolites. The definition of metal-organic frameworks and their structural characteristics, such as the secondary building units and crystal flexibility, are also reviewed.

Chapter two discusses the use of metal-organic frameworks in water treatment processes. Three basic criteria of choosing metal-organic frameworks for this application are defined. Compound [Cu3(BTCh(OH2h]n (BTC = 1,3,5-benzenetricarboxylate), referred as Cu3, is chosen accordingly for investigation. A novel microwave synthesis of Cu3 is developed. Absorption experiments with
Organic solutes, such as alcohols, phenol and aniline, using Cu3 have been investigated by 1H-NMR spectroscopy. It revealed Cu3 preferentially absorbs to hydrophobic solutes. The water stability and regeneration of Cu3 have also been studied. A new Fe based polymer-structural material [Fe(O)(OOCCH20CH2COOh(H20h](OOCCH20CH2COOJ0_5, referred as Fe OF,
has been designed and synthesised with the aim of removal of phosphate from water. Static and continuous flow absorption tests reveal Fe-MOF is able to remove phosphate from water. In addition, an unexpected metal-organic gel, referred as Fegel, has been obtained. Macroporous polymethyl methacrylate has been synthesised by using this gel as a template.

Chapter three describes the synthesis of some ne metal-organic frame types of ligands, isonicotinlc acid (INA) and H3BTC, are used. The new metal-INAtype frameworks, examples being Mn(fNAh · 0.5EtOH · O.SH2O 3 and [Co(INA)2]·0.5EtOH 4, [Co(INA)2)'0 .5H2O 5, [Co(INA)2]'0.5Pr1OH·H2O 6, revealed a new structural flexibility behaviour in MOFs, that is, the pyridyl rings in these structures can rotate freely between 'open' and 'closed' positions to let the guests move in and out of the channels. Further studies of compound 4 displayed unprecedented expansion-contraction behaviour during sorption and desorption process of guest molecules. Derivatives of INA, such as 3-ftuoro-isonicotinic acid (INA-F), 3-methyl-isonicotinic acid (INA-Me) and quinoline-4-carboxylic acid (INA-Bz), formed further three new frameworks with Co ions: Co{INA-F)£0.5MeOH 7, Co(INAMe) 22MeOH 8, Co(INA-Bz)2.H2O 9. Crystallographic analysis of 7-9 revealed relationships between steric effects of the organic linkers and the adopted framework structure. Two interpenetrated frameworks, Zn(INA)2.0.5EtOH.0.5H2O 10 and Zn(L 1 )2.MeOH (L 1 = 4-[(Pyridine-4-methylene)-amino]-benzoate) 11 , were also obtained. Framework 11 revealed an interesting relationship between the inclusion of solvent and the chirality of the framework. Highly novel anionic frameworks, [Me2NH2][Zn2(BTC)(HBTC)](DMF) 13 and [EhNH2][Zn(BTC)0 .5H2O] 14, were synthesised by the reaction of Zn(II) ions with H3BTC under solvothermal conditions. Cation exchange of framework 13 was conducted and revealed that it occurred via dissolution and recrystalisation.

Chapter four contains the references and experimental details of the above chapters.
Date of AwardJul 2005
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorStuart James (Supervisor) & Frederic Meunier (Supervisor)

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