Final Report Summary - INANOMOF (Multifunctional micro- and nanostructures assembled from nanoscale metal-organic frameworks and inorganic nanoparticles) In our ERC-funded project InanoMOF, we developed a series of new composite adsorbents via controlled assembly of nanoscale porous Metal-Organic Frameworks (nanoMOFs) and functional inorganic nanoparticles (INPs). The resulting nanoMOF@INP composites marry the functional porosity of MOFs (e.g. ZIF-8, UiO-66, UiO-66-SH, etc.) with the unique properties of INPs (e.g. Au, iron oxide, Pt, Pd, CeO/Cu, CeO2, and hollow Pt, Pd and Au NPs, etc.). By developing new synthetic methodologies (e.g. nanostructure template synthesis, desymmetrization at interfaces, and spray-drying), we were able to fabricate two type of composites: discrete nanoscale composites and higher-level superstructures or beads. The discrete composites were synthesized by either coupling the INPs onto the surface of the MOF particles, or encapsulating the INPs within the MOF particles. Remarkably, we then improved upon the complexity of the latter composites by designing onion-like systems in which we grow alternating layers of MOFs and INPs. Following this approach, we were able to obtain nanoMOF@INP systems containing more than one type of functional INPs (e.g. Au and Pd NPs). In contrast, we synthesized the higher-level nanoMOF@INP superstructures and beads by spray-drying. This new method, which we have patented and have subsequently licensed to a European SME, is based on introducing a continuous-flow reactor at the entrance of the spray-dryer. This continuous process yields dried MOF particles shaped as microspherical superstructures or beads that incorporate the INPs within their matrices.Impressively, our diverse new nanoMOF@INP composites exhibit the inherent porosity of the constituent MOFs as well as the inherent functionality (e.g. magnetism, optics, etc.) of the constituent INPs, thus demonstrating strong potential for use in environmental and biological applications. For example, our nanoUiO-66-SH@CoNP composite is extremely efficient at removing mercury from water, removing 99% at 10 ppm, and after extraction, can easily be removed using a simple magnet. Likewise, our nanoUiO-66-SH@CeO2NP beads can simultaneously remove multiple heavy-metal ions from water with high efficiency. In fact, we have tested beads on real water samples, finding that they decrease the metal content (As(III and V), Cd(II), Cr(III and VI), Cu(II), Pb(II) and Hg(II)) to levels down to 0.25 ppb, thus bringing the samples to World Health Organization standards for metal-ion content in drinking water. Similarly, our nanoZIF-8@hollow_PdNP composite is very efficient at catalyzing the reduction of 4-nitrophenol, a highly-toxic water pollutant. In the field of biological applications, we recently engineered a new iodine-delivery composite system, which we envision for use in a new family of anti-microbial coatings. This system, a core-shell composite based on a single hollow Au NP encapsulated within nanoUiO-66, can store and stabilize iodine at very high concentrations (up to 1.7 mg iodine/mg MOF) and can release it two ways: slowly and passively at low concentrations; or, upon triggering by near-infrared (NIR) light, rapidly and actively high concentrations. The methodologies that we developed in InanoMOF have furnished access to myriad composite materials with demonstrated utility in environmental and biological applications. Moreover, with these methodologies, we can now access an endless variety of composite materials for various other applications. For instance, preliminary results have shown that nanoMOF@INP composites can also perform well as catalysts (e.g. for conversion of CO or CO2) or be used to create microporous nanomotors. Exploratory work has also confirmed that our developed methodologies can be implemented to generate other families of composites containing other porous materials (e.g. covalent-organic frameworks [COFs]), or of inorganic salts, thereby expanding the design space for composite materials.
