Title:
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Novel Crystalline Framework Materials
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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.
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