Strategic immobilisation of catalytic metal nanoparticles in metal-organic frameworks
Abstract
This thesis describes the synthesis, characterisation and catalytic testing of
multifunctional immobilised metal nanoparticle in metal-organic framework (MOF)
materials. Combining the activity of metal nanoparticles with the porosity and Lewis
acidity of metal-organic frameworks provides a single catalytic material which can
perform multi-step reactions.
Strategies to immobilise the metal nanoparticles within the metal-organic frameworks
have been investigated. Immobilisation has been achieved by applying three different
methodologies. First, deposition of metal nanoparticle precursors within mesoporous
MOFs is discussed. Chapter 3 shows the effectivity of the double solvents deposition
technique to achieve dispersed and small nanoparticles of around 2.7 nm. The best
system combined Pd nanoparticles with MIL-101(Cr). This system was further
investigated in tandem reductive amination catalysis, discussed in Chapter 4, to
investigate the activity and selectivity provided by these multifunctional catalysts.
Another immobilisation technique was performed by coating Pd decorated SiO₂
spheres with a MOF layer. Using this technique, MOF was grown cyclically in solution,
providing tuneable shell thicknesses of MOF on the metal nanoparticle decorated
oxide spheres. While the homogeneity of the MOF shell needs more optimisation, it
was determined that the surface charge on the spheres played an important role in the
growth of MOF in the desired location.
Finally, the third immobilisation technique is the core-shell growth of MOF on colloidal
metal nanoparticles. Polymer-capped metal nanoparticles with well-defined shapes
were synthesised and characterised. From here, the optimisation of conditions for
core-shell growth of UiO-66 and MIL-100(Sc) were investigated. Conditions which
provided the desired core-shell morphology were found for both MOF types. These
materials were then subsequently used in tandem reductive amination catalysis and a
more straightforward styrene hydrogenation. It was shown that the metal
nanoparticles remain active catalysts within either MOF shell and the MOF shell
stabilises the metal nanoparticle and acts as a Lewis acid catalyst.
Type
Thesis, PhD Doctor of Philosophy
Collections
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.