Understanding your support system: the design of a stable MOF/polyazoamine support for biomass conversion

20 September 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Introducing oligomeric or polymeric units into metal-organic frameworks (MOFs) can result in composites that have significantly improved properties when compared to the individual MOF or polymer building blocks. With such synergy in mind, this work presents the design of a novel MOF/polyazoamine support that is used to stabilize Pd NPs. The resulting composite catalyst, tested in the reductive amination of levulinic acid, is found to have a markedly improved lifetime when compared to just the MOF or polymer support containing Pd. It is demonstrated, for the first time, that the lifetime enhancement stems directly from the polymer, which plays a dual role: i) the oligomer stabilizes the MOF support through the elimination of certain vibrational modes associated with the framework ligand and likely pore-filling effects in the largest MOF pore, and ii) the Lewis base functionality on the oligomer backbone binds to the surface of the Pd NPs, thus, increasing their activity and inhibiting their aggregation. Several complementary spectroscopic (IR, XPS, Raman spectroscopy) and computational tools (pore space and topology analysis, molecular mechanics, and density functional theory simulations) were used to describe the nature of the MOF-oligomer interaction and identify the most likely location of the polymer within the MOF pore.

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Supporting information including discussions of general experimental details, synthetic procedures, catalysis protocols, figures of PXRD patterns, N2 adsorption isotherms, thermogravimetric analyses, IR spectra, XPS spectra, SEM images, mass spectrum, TGA profiles, FT-IR spectra, tables of calculated polymer loadings, peak quantifications for the Pd 3d, C 1s and N 1s regions of the XPS spectrum etc.
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