Pyrene-based metal organic frameworks: from synthesis to applications

Pyrene is one of the most widely investigated aromatic hydrocarbons given to its unique optical and electronic properties. Hence, pyrene-based ligands have been attractive for the synthesis of metal–organic frameworks (MOFs) in the last few years. In this review, we will focus on the most important characteristics of pyrene, in addition to the development and synthesis of pyrene-based molecules as bridging ligands to be used in MOF structures. We will summarize the synthesis attempts, as well as the post-synthetic modifications of pyrene-based MOFs by the incorporation of metals or ligands in the structure. The discussion of promising results of such MOFs in several applications; including luminescence, photocatalysis, adsorption and separation, heterogeneous catalysis, electrochemical applications and bio-medical applications will be highlighted. Finally, some insights and future prospects will be given based on the studies discussed in the review. This review will pave the way for the researchers in the field for the design and development of novel pyrene-based structures and their utilization for different applications.

Taking lanthanides out of isolation: tuning the optical properties of metal-organic frameworks

Samantha Lynn Anderson, Gloria Capano, Maria Fumanal Quintana, Andrzej Gladysiak, Nestor Guijarro Carratala, Christopher Patrick Ireland, Stavroula Kampouri, Kevin Sivula, Berend Smit, Kyriakos Stylianou, Davide Tiana

Metal organic frameworks (MOFs) are increasingly used in applications that rely on the optical and electronic properties of these materials. These applications require a fundamental understanding on how the structure of these materials, and in particular the electronic interactions of the metal node and organic linker, determines these properties. Herein, we report a combined experimental and computational study on two families of lanthanide-based MOFs: Ln-SION-1 and Ln-SION-2. Both comprise the same metal and ligand but with differing structural topologies. In the Ln-SION-2 series the optical absorption is dominated by the ligand and using different lanthanides has no impact on the absorption spectrum. The Ln-SION-1 series shows a completely different behavior in which the ligand and the metal node do interact electronically. By changing the lanthanide in Ln-SION-1, we were able to tune the optical absorption from the UV region to absorption that includes a large part of the visible region. For the early lanthanides we observe intraligand (electronic) transitions in the UV region, while for the late lanthanides a new band appears in the visible. DFT calculations showed that the new band in the visible originates in the spatial orbital overlap between the ligand and metal node. Our quantum calculations indicated that Ln-SION-1 with late lanthanides might be (photo)conductive. Experimentally, we confirm that these materials are weakly conductive and that with an appropriate co-catalysts they can generate hydrogen from a water solution using visible light. Our experimental and theoretical analysis provides fundamental insights for the rational design of Ln-MOFs with the desired optical and electronic properties.

2020

Catalyst design for C-O bond hydrogenolysis of renewable materials.

Antoine Philippe Van Muyden

Anthropogenic carbon dioxide emissions leading to climate change require to use of renewable carbon sources such as CO2 and biomass which differ from fossil resources by having a higher number of oxygen atoms. Therefore, catalytic C-O bond cleavage will play a pivotal role in their conversion into carbon neutral fuels, materials and chemicals. This thesis will focus on the most challenging substrate for selective C-O bond hydrogenolysis, diaryl ether present in lignin (i.e. one of the components of biomass), summarise the state of research and improve the comprehension in the characteristics a catalyst requires to selectively cleave these bonds without altering other functionalities. We showed that the modification in the electronic state and the resulting polarity between two different metals present in a bimetallic nanoparticle favour the selectivity towards hydrogenolysis of a polar C-O bonds over aromatic ring hydrogenation. In addition, we demon-strate that single metal sites cannot hydrogenate an aromatic ring and hence are selective. Final-ly, we applied our knowledge in C-O bond cleavage in CO2 conversion using propylene carbonate as a relay molecule to produce propylene glycol and methane.

EPFL2020

Luminescent, porous, metal-organic crystals: Design, synthesis, and applications

Fatmah Ebrahim

The work presented in this thesis is focused on the design and discovery of new luminescent, porous, crystalline materials for targeted applications. In particular, we focus on luminescent Metal-Organic Frameworks (MOFs) and Organic Molecules of Intrinsic Microporosity (OMIMs), both belonging to emerging classes of synthetic materials that are particularly promising due to their porosity, modularity, and the many dynamic photophysical processes that can be exploited within them. While there is great potential for these types of materials, their relatively recent discovery, less than two decades prior to the writing of this thesis, means that they are still in early stages of development and so very few examples exist that demonstrate the potential for real-world applicability. Challenges persist in achieving targeted design, high stability, or processing for integration into devices. The aim of this thesis is consider new ways of strategically designing MOFs and OMIMs that may be carried a step closer to real-world application. With problems like excess energy consumption and the depletion of clean air and water supplies on the rise in todayâs world, applications that can have a positive impact on the environment are of particular interest. We present a luminescent MOF that is capable of detecting trace amounts of fluoride contaminations in drinking water down to the parts per billion (ppb) range. The interactions of this MOF with fluoride in aqueous solutions are simultaneously electrostatic and specific in nature because of the carefully designed structure of its active site. This allows the material to be easily regenerated and used over 10 cycles, setting it apart from most existing molecular and polymeric fluoride sensors. We combined our MOF with a portable prototype sampling device that was designed and built in-house to measure fluoride concentrations in natural groundwater samples taken from three different countries, with the results showing excellent agreement with ion chromatography analysis. The strategy that we use to obtain this reversible yet selective interaction can be applied to the design of new MOFs that work on a similar principle. In addition, we present a new OMIM that exhibits broad spectrum, tuneable white light emission. The structural components and pore environment of the OMIM contribute to it having a high quantum yield in addition to tuneability that can be controlled by guest molecules. Using this material, we obtain the highest thus-far reported value of photoluminescence quantum yield for a single-species white-light emitter, with a nearly pure-white emission colour. This has promising implications for the fabrication of new, energy-efficient Organic Light-Emitting Diode (OLED) devices. In addition, introducing structural changes to the base ligand of this OMIM will allow us to obtain a greater range of colour tuneability as well as new features of guest-host chemistry.

EPFL2021

Luminescent, porous, metal-organic crystals: Design, synthesis, and applications

Fatmah Ebrahim

EPFL2021

Taking lanthanides out of isolation: tuning the optical properties of metal-organic frameworks

2020