Hybridization of Synthetic Humins with a Metal–Organic Framework for Precious Metal Recovery and Reuse

Abstract

The number of synthetic strategies used to functionalize MOFs with polymers is rapidly growing; this stems from the knowledge that non-native polymeric guests can significantly boost MOF performance in a number of desirable applications. The current work presents a scalable and solid-state method for MOF/polymer composite production. This simple method constitutes mixing a MOF powder, namely, Fe-BTC (BTC = 1,3,5-benzenetricarboxylate), with a biomass-derived solid monomer, 5-hydroxymethylfurfural (HMF), and subsequently heating the solids; the latter promotes both solid-state diffusion of HMF into the MOF and the formation of polymeric humin species with a high density of accessible hydroxyl functionality within the MOF pore. The resulting composite, Fe-BTC/humin, was found to selectively extract Ag + ions from laundry wastewater. Subsequent reduction of the Ag + species yields a novel catalyst, Fe-BTC/humin/Ag, that is able to drive the organic transformation of cinnamaldehyde in a highly selective manner. Moreover, the catalyst exhibited recyclability up to five cycles, which is in contrast to the Fe-BTC/Ag catalyst without the humin-based polymer. It is envisioned that MOF/polymer composites that are able to selectively extract precious metals from liquid waste streams can be used for the future production of sustainable catalysts; this work was aimed at demonstrating a proof of concept in this regard. Moreover, this study brings more understanding of the impact that MOFs can have on polymer functionalities. Understanding the polymer structure and how it can be manipulated will help us realize the high degree of future potential of this distinct class of composite materials.

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

“…The Cu-TDPAT/PAD support was then functionalized with Pd NPs according to a method that we previously developed. 15 For this, the Cu-TDPAT/PAD powder was first dispersed in methanol at room temperature, and then an aqueous solution containing Pd(NO3)2 was added dropwise. Subsequent stirring at room temperature for 3 hours yields the desired Cu-TDPAT/PAD/Pd catalyst (see the supplementary information for additional details).…”

“…Due to the hinge-like connectivity between the metal and ligand, the material normally transitions from a large pore to a narrow pore structure upon solvent removal; however, the added polymer induced reticular stiffness, thereby inhibiting the narrow pore transition. 11 In other studies, it was demonstrated that the introduction of oligomers, which have a high density of Lewis base functionality on their backbone, can help stabilize metal nanoparticles (NPs) grown inside MOF pores; [14][15] this can extend the catalyst lifetime when compared to MOF-NP composite excluding the polymer. These reports show that the eventual degradation of the composite catalyst is correlated with the decomposition of the MOF structure itself, which, in turn, allows the release and aggregation of the catalytically active NPs.…”

“…These reports show that the eventual degradation of the composite catalyst is correlated with the decomposition of the MOF structure itself, which, in turn, allows the release and aggregation of the catalytically active NPs. [14][15] Given this, we have begun varying the MOF and polymer building blocks in an effort to optimize catalyst performance and lifetime in targeted chemical reactions.…”

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

“…These reports show that the eventual degradation of the composite catalyst is correlated with the decomposition of the MOF structure itself, which, in turn, allows the release and aggregation of the catalytically active NPs. 14,15 Given this, we have begun varying the MOF and polymer building blocks in an effort to optimize catalyst performance and lifetime in targeted chemical reactions. Herein, a newly designed MOF−polymer composite catalyst that combines the two aforementioned aspects is reported; a single oligomeric component that simultaneously stabilizes both the MOF and Pd NPs is found to significantly boost catalyst lifetime.…”

Solid-state synthesis of a MOF/polymer composite for hydrodeoxygenation of vanillin

“…24 While the field of MOF-polymer composites is rapidly growing, there is limited understanding in the literature regarding the structure-derived function of such materials nor how the MOF directs the polymer formation. 25 Given this and that recent work demonstrates that the growth of polymers inside MOF pores can have profound effects on the structural properties of the resulting polymer, 26 we have set out to understand the structural properties of PFT liberated from the MOF pores. Also, to further understand the consequence that the MOF has on the polymer structure, a control bulk polymerization reaction was also run with the monomers excluding the MOF.…”