Abstract
Metal-organic frameworks (MOFs) are hybrid materials composed of inorganic metal nodes (ions or clusters) coordinated by organic linkers. Their high surface area and tunable pore chemistry make them attractive for applications such as sensing, separations, catalysis, and storage. Zirconium (Zr)-based MOFs are especially promising owing to their exceptional chemical and thermal stability, which arises from strong Zr-O bonds and high node connectivity. However, MOFs are typically synthesized as brittle powders, limiting their processability and, in some applications, their performance. Incorporating polymers offers a route to addressing both limitations by imparting flexibility and processability and by introducing new functionality. This dissertation employs in situ growth of Zr-MOFs in the presence of polymers, using scalable synthesis routes, to produce polymer-MOF composites in various form factors, including thin films, textiles, and powders, for diverse applications in sensing, protective clothing, and decarbonization.
In Chapter 2, we utilize a meniscus-guided coating technique called solution shearing to fabricate piezoelectric thin films of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))-UiO-66 polymer-MOF composite. We study how varying the polymer concentration during MOF synthesis affects thin-film properties, including crystallinity, surface coverage, and piezoelectric performance. Incorporating P(VDF-TrFE) increases the film’s surface coverage from 70% to full coverage while enhancing the piezoelectric response of the composites. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy reveals closer proximity between P(VDF-TrFE) and the UiO-66 framework in the in situ-synthesized composites than in those prepared by physical mixing, supporting a combined surface-coating and pore-infiltration model. Overall, this chapter demonstrates the potential of solution shearing as a scalable technique for fabricating functional polymer-MOF composite thin films.
Moving beyond thin films, Chapter 3 extends the same in situ strategy to textile substrates, synthesizing UiO-66 and UiO-66-NH₂ on polyester and cotton using a sequential dip-coating (SQD) technique combined with a roller system to mimic industrial roll-to-roll processing. Large-area (~55 inch²) UiO-66-polyester masks are synthesized that meet the ASTM F3502 Level 1 criteria for particulate matter (PM) filtration and continue to meet Level 1 criteria after 25 washing-drying cycles, supporting their use as reusable facial coverings. In parallel, UiO-66-NH₂-coated fabrics demonstrate significant degradation of nerve agents, thereby extending the application of synthesized MOF-fabrics for defense-related uses.
Chapters 4 and 5 focus on the development of polymer-MOF composites for decarbonization. In Chapter 4, aiming to enhance the CO₂ capture capacity of pristine MOF, we synthesize UiO-66-NH₂ in the presence of an amine-rich polymer, polyethyleneimine (PEI), via an aqueous synthesis route. We study how varying PEI concentration affects the MOFs’ porosity and crystallinity, as well as the composites’ CO₂ uptake capacity. The composite with the lowest PEI loading shows the highest CO₂ uptake, exceeding that of pristine UiO-66-NH₂, whereas higher PEI loadings improve storage stability, revealing a composition-dependent trade-off between capacity and stability. Because CO₂ capture and storage (CCS) entails economic and environmental costs associated with CO₂ desorption, transport, and storage, we develop a ternary Cu-PANI@UiO-66-NH₂ composite in Chapter 5. This composite combines copper nanoparticles (CuNPs), polyaniline emeraldine salt (PANI-ES), and UiO-66-NH₂ as an integrated CO₂ capture and utilization (ICCU) platform, aiming to capture CO₂ and convert it to value-added products via the electrochemical CO₂ reduction reaction (eCO₂RR). Incorporating PANI-ES enhances the electrical conductivity of the composites, while the successful incorporation of well-distributed CuNPs throughout the composite is a promising indicator for future CO₂ conversion work, since copper is the catalytic site for eCO₂RR. This chapter shows that the porosity and conductivity can be balanced by tuning PANI-ES composition and establishes the ternary composite as a promising scaffold for ICCU. Together, this work shows that in situ formation of zirconium MOFs in the presence of polymers is a versatile strategy for producing polymer-MOF composites across multiple form factors, advancing their use in sensing, protective clothing, and decarbonization.
