Water‐Based Assembly of Polymer–Metal Organic Framework (MOF) Functional Coatings

Abstract

Metal organic frameworks (MOFs) have gained attention for their porosity, size selectivity, and structural diversity. There is a need for MOF-based coatings, particularly in applications such as separations, electronics, and energy; yet forming thin, functional, conformal coatings is prohibitive because MOFs exist as a powder. Layer-by-layer assembly, a versatile thin film coating approach, offers a unique solution to this problem, but this approach requires MOFs that are water-dispersible and bear a surface charge. Here, these issues are addressed by examining water-based dispersions of MIL-101(Cr) that facilitate the formation of robust polymer-MOF hybrid coatings. Specifically, the substrate to be coated is alternately exposed to an aqueous solution of poly(styrene sulfonate) and nano MIL-101(Cr) dispersion, yielding linear film growth and coatings with a MOF content as high as 77 wt%. This approach is surface-agnostic, in which the coating is successfully applied to silicon, glass, flexible plastic, and even cotton fabric, conformally coating individual fibers. By contrast, prior attempts at forming MOF-coatings are severely limited to a handful of surfaces, require harsh chemical treatment, and are not conformal. The approach presented here unambiguously confirms that MOFs can be conformally coated onto complex and unusual surfaces, opening the door for a wide variety of applications.

Transport of Polymer-Coated Metal-Organic Framework Nanoparticles in Porous Media

“…14 Namely, although it may be electrostatically-favorable for nanoparticles to adsorb to surface sites, thick electric double layers (EDL) at low ionic strength solution conditions may impede nanoparticle approach to attachment sites. 14 This paradigm is consistent with our experimental setup, as the MOF nanoparticles are all dispersed in ultrapure water 27 to make nano uids. Therefore, as the ionic strength increases, we would expect NP retention to increase dramatically relative to polymercoated MOFs, like NP-PSS-70K, as the EDL becomes thinner.…”

Chemically Active, Porous 3D-Printed Thermoplastic Composites

“…The ability to fine-tune the crystalline structure of a MOF through judicious selection of both the organic linker moieties and metal ion centers allows the modulation of catalytic activities, pore sizes for molecular storage and separations, and luminescent properties for sensing applications. − One outstanding hurdle to the commercial and industrial applications of MOFs is their powder form as pure crystalline materials. , For incorporation into devices, ideally MOF crystallites could be integrated into a composite platform to improve the mechanical properties but still retain their desired chemical reactivity characteristics by the preservation of their crystallinity, porosity, and surface area (SA). To this end, MOFs have been incorporated into polymers and cast into films or formed into “mixed-matrix membranes” (MMMs), grown in situ on the surface of other materials, deposited onto surfaces using a layer-by-layer strategy, electrospun into mats, or inkjet-printed onto surfaces. − In some cases, the growth of a MOF layer directly on a preformed substrate may be adequate. However, issues related to the chemical compatibility of the underlying structure and the MOF synthetic procedure and the potential for poor adhesion of the MOF to the prefabricated structure motivate the development of novel methods to disperse pregrown MOFs entirely throughout a composite structure.…”

Retrospective on Recent DOE-Funded Studies Concerning the Extraction of Rare Earth Elements & Lithium from Geothermal Brines (Final Report)

“…The final report does not include a full description of the MOF material used, but supporting material from the GDR and related publications suggest the MOF is similar or identical to MIL-101, a chromium terephthalate metal-organic framework (Bhattacharjee et al, 2014;Elsaidi et al, 2016;De et al, 2017;Elsaidi et al, 2017;McGrail, 2017). MIL-101, named for the Institut Lavoisier (France), is comprised of trimeric chromium(III) octahedral clusters interconnected by 1,4-benzenedicarboxylates, resulting in a highly porous 3-dimensional structure.…”