Understanding Your Support System: The Design of a Stable Metal–Organic Framework/Polyazoamine Support for Biomass Conversion

Abstract

Introducing oligomeric or polymeric units into metal–organic frameworks (MOFs) can result in composites that have significantly improved properties when compared with 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 nanoparticles (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, X-ray photoelectron spectroscopy, Raman spectroscopy) and computational tools (pore space and topology analysis, molecular mechanics, and density functional theory simulations) are used to describe the nature of the MOF–oligomer interaction and identify the most likely location of the polymer within the MOF pore.

The Chemistry of Metal Organic Framework Materials

“…More recently, MOF glasses, a disordered form of MOFs, are finding niche applications. This virtual collection catalogues recent MOF advances featured in Chemistry of Materials from 2022 to 2023, − with an accompanying editorial by Laura Gagliardi and Omar Yaghi that outlines three critical future directions for MOFs …”

“…Mere soaking in HgCl 2 solution transforms an interpenetrated Zn MOF into a noninterpenetrated phase. Such inclusion of active species into the MOF has been exploited in catalysis by Queen and co-workers , who emphasize MOF–polymer composites as a superior support for catalytic Pd nanoparticles . The study by Kim and co-workers highlights the ability of MOFs to form heterogeneous single-site Ir catalysts matching the activity of the homogeneous ones with all other added advantages …”

“…Such inclusion of active species into the MOF has been exploited in catalysis by Queen and co-workers, who emphasize MOF−polymer composites as a superior support for catalytic Pd nano-particles. 15 The study by Kim and co-workers highlights the ability of MOFs to form heterogeneous single-site Ir catalysts matching the activity of the homogeneous ones with all other added advantages. 16 Shen et al strategized the inclusion of the spin crossover Fe 3+ complex as a guest into Zr-MOF (MOF-808), giving rise to near-room temperature hysteresis, which unusually was independent of the loading and the particle size of the MOF−composite.…”

Interfacing metal organic frameworks with polymers or carbon-based materials: from simple to hierarchical porous and nanostructured composites

“…Cu-TDPAT with TDPAT 6− = 2,4,6-tris-3,5-dicarboxylphenylamino)-1,3,5-triazine) to prepare a novel Cu-TDPAT/polyazodianiline(PAD) catalyst for biomass conversion. 60 After the loading of 4,4′-azodianiline monomers in the MOF pores, their subsequent reaction with CO 2 molecules was catalysed by Cu 2+ centres of the MOF and this led to the formation of short oligomeric chains confined in the pores of the MOF. 60 Such oligomers consisted of azodianiline moieties bridged by urea linkages.…”

On the origin of the combinatorial complexity of the crystal structures with 0D, 1D, or 2D primary motifs

“…10 The complexity of the metal-organic framework may influence the number of adsorption sites required for molecular simulations. 11 Molecules that are weakly or non-phosphorescent in fluid solution can switch to room temperature phosphorescence upon aggregation due to (i) rigidification by crystallization or by encapsulation in a polymeric matrix and (ii) interaction with other molecules of the same type (self-aggregation) or a different type by taking advantage of heavy-atom effects. 12 The amount of the "chemical" information resulting from the composition of E…”