Novel Crystalline Framework Materials

Owen Carter, Benjamin (2007) Novel Crystalline Framework Materials. PhD thesis, University of Liverpool.

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Abstract

This t.hesis describes the synthesis and characterisation of metal-organic framework matenals based on cobalt and nickel salts with rigid organic ligands. 'It also contains an account of synthetic and catalytic work towards the incorporation of rhodium into existing frameworks. Chapter 1 provides an introduction to the topic, covering background on the zeolites, an account of the development of frameworks and their applications in modern chemistry, and specific examples relating to the novel frameworks described in later chapters. Chapter 2 covers the synthetic and analytical techniques used to prepare and characterise these materials. ' Chapter 3 describes the detailed crystal structures of five entirely novel frameworks based upon nickel salts and bipyridylligands (4,4'-bipyridine (bipy) and 1,4bis( 4-pyridyl)benzene (3RB». Nickel (II) nitrate and 3RB combine under solvothermal conditions to produce a dense material formed of herringbone layers, [Nb(N03M3RBh] (BC160), with no extra-framework voids. The substitution of nickel nitrate for the equivalent sulphate, combined with room temperature diffusion techniques gives rise to an inclined interpenetrated phase of cross-linked dimer chains, [Nb(S04h(3RBh(H20)] • 2(CH30H) • 3(H20) (BC261). This material displays a 49% extra-framework volume, but suffers from an instability to guest loss. The use of bipy in place of 3RB under similar conditions generates a three-dimensional array of Ni-bipy square grids, pillared by sulphate anions, [Ni(S04)(bipYh] • 3(MeOH) • 3(H20) (BC402). The uniform channels running through the infinite lattice impart an extra-framework volume of 50%. However, given the presence of an irremovable impurity in the as-made crystalline phase, this material presents no opportunities to explore its porous applications. The use of microwave solvothermal techniques produces a new crystalline material, a possible precursor for BC402 above based on the same reactants, [{Ni(bipy)(S04h(H20h} {Ni(bipy)(H20)4} • Bipy] • 3(H20) (BC482). The dense crystal structure comprises two species of one-dimensional chain, which stack in alternating layers along with unbound intercalating bipy molecules. The material possesses no void spaces, and will not undergo phase transition to the BC402 structure. Finally, chiral aspartic acid (Asp) is combined with nickel nitrate and 3RB under solvothermal conditions to form an extended analogue of a bipy-based structure, Nb(L-Asph(3RB)· x(3RB) (BC533_3). Despite a 19% extra-framework volume, this material possesses unbound 3RB occupying its channels. Chapter 4 explores two routes toward catalytic heteronuclear rhodium frameworks. (1) Solvothermal doping of rhodium dimers into CU3(btch(H20h (H3btc = 1,3,5-benzenetricarboxylic acid). Catalytic activity toward the hydrogenation of 1-hexene is investigated, and turnover frequency in the doped frameworks reaches 0.15 molhexane/ mol-Rh/hr. (2) Synthesis of rhodium terephthalate paddlewheel units into existing metal carboxylate frameworks. Discrete paddlewheels are produced, and room temperature and solvothermal techniques toward new heteronuclear frameworks are explored. Chapter 5 covers the synthesis of a further five novel frameworks, based upon a (10,3)-a network topology. New materials are synthesized solvothermally from cobalt nitrate, btc, methyl-pyridines and 1,2-propanediol (1,2-pd) as analogues to existing nickel frameworks, producing four-fold and two-fold interpenetrating nets: C03(btch(4picolineM1,2- pd)6 (BC144) and COJ(btch(3-picoline)&(1,2-pdh (BC143) respectively. Further variations on BC143 are explored through the use of alternative pyridines (resulting in the successful synthesis of Nh(btch(3-ethylpyridine)6(1,2-pdh (BC198» and diols, producing C03(btch(3-picolineM1,2-pentanediolh (BC173) and C03(btch(3picoline) 6(1,2-hexanediolh (BC174). The final two frameworks possess channels functionalised by diol alkyl chains, with a subsequent reduction in void volume.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	20 Oct 2023 09:24
Last Modified:	20 Oct 2023 09:46
DOI:	10.17638/03174400
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3174400