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Metal-Organic Frameworks (MOFs)
The NC-Jeong group is developing the chemical science and applications using the precise assembly of materials by the molecular building block approach. For this, we use supramolecular chemistry where molecular building blocks (organic molecules, inorganic clusters and complexes, proteins, peptides, and dendrimers) are linked into extended frameworks with strong bonds. This chemistry allows us to translate the high functionality of molecules into solids without losing the robustness needed for making useful materials and the dynamics and molecular flexibility required for highly functional materials. Thus, in our group new materials are created by 'stitching' metal-ions and metal complexes with organic linkers to make extended porous frameworks called metal-organic frameworks (MOFs). These are all new classes of porous crystals studied for their applications to clean energy storage and generation, clean water generation and delivery, supercapacitors, thermal batteries, ion-conductivity, and electronic conductivity.
Our research is focused on using metal complexes and metal-oxide clusters as building units in the synthesis of MOFs. These inorganic units are copolymerized with organic linkers to make MOFs and related porous crystals. An important direction pertains to exposing metal coordination sites within the pores. Here, terminal ligands are found on the metal connectors at axial position. These ligands can be removed with full preservation of the structure, thereby leading to open metal sites in low coordinated metals. The electronic and steric nature of these open metal sites makes them ideal for studying chemical science, for examples, discovering weak coordination bonding, coordination exchange, non-radiative thermal relaxation phenomena, and hydrogen bonding.
Membrane & Film Technology
Increase in the world's population has increased demand for both eco-friendly energy sources and high-quality drinking water. The desalination of seawater is considered as a viable option to produce large amounts of clean drinking water, however, current processes to achieve this large amounts consumption of energy and the porous materials used to filter seawater lack fine control over pore-size. Ion-exchange membranes will be a promising key materials in the process of seawater desalination. Proton-exchange membrane fuel cells have shown the potential to reduce the environmental impact in energy consumption, but current technology for the applications are limited by high costs and short lifetimes of membranes. In our group, we seek to apply supramolecular chemistry to solve these issues. Currently, we are investigating a series of hybrid polymeric porous membranes and films, alongside chemically interlocked inorganic polymers, which incorporate various redox-active building blocks, to produce the next generation of water desalination, fuel-cell membranes, and electronic film devices.
Ion Transport System
An ultimate goal in proton-exchange membrane fuel cells, lithium ion batteries, and supercapacitors is to find better ionic conducting systems. MOFs can be considered as ideal systems for these applications because their potentially high ion transport abilities. Meanwhile, porous carbon materials have been used for commercial lithium ion batteries and supercapacitors that operate by storing charge on electrochemical double layers. By contrast, pseudocapacitors typically made from metal oxides can store charge by redox reactions. These classes of supercapacitor have both merits and demerits: carbon-based materials operate at very high charge/discharge rate with long lifecycle but have low capacitance, while metal oxide materials have high capacitance but their redox reactions lead to low lifecycle. We are working on ways of bridging the gap separating these two classes, using MOFs.
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