Inorganic Seminar - Minyoung Yoon

The Inorganic Seminar Series presents: Minyoung Yoon

Kyungpook National University

Host: Simon Humphrey

Title: Toward Utilization of Hydrogen as a Fuel: Transport of Protons in Solid-State Confined Space and Hydrogen Storage in Liquid Organic Media

Refreshments served at 3:15pm

Location: WEL 2.122

Coordination polymers (CPs), formed by connecting metal ions with ligands, hold significant promise as unique magnetic systems. Especially notable are CPs utilizing transition metal ions with unpaired electrons, such as Cr, Mn, Co, and Ni, which can form multi-dimensional paramagnetic metal chains. This arrangement induces aligned electron spins within CPs, leading to magnetic interactions that amplify or neutralize the magnetic moment. As a result, CPs with well-defined crystalline structures are valuable for exploring magnetic properties through structural analysis. In this study, we present an in-depth analysis of the magnetic properties of water-coordinated CPs, specifically [M(HCO₂)₂(H₂O)₂]_n, where M can be either Co(II) or Ni(II), using neutron experiments. Interestingly, exposure to high humidity triggered a remarkable structural transformation in non-hydrated CPs, leading to their irreversible conversion into a hydrated state. We successfully determined the crystal structures of both the non-hydrated and hydrated forms of Ni-formate. Our focus was on unraveling the magnetic structure of metal-formate to comprehend how the inclusion of adsorbed or coordinated water molecules influences spin alignment within CPs. Furthermore, we plan to obtain and compare crystal structures through single-crystal analysis at low and high temperatures to understand better the peculiar contraction along the c-axis observed with increasing temperature. In addition, a new technology should be developed to facilitate the delivery and storage of H₂. Unlike the generation of H₂, the storage process requires the development of storage media (liquid organic hydrogen carrier; LOHC) and hydrogenation/dehydrogenation catalysts. A novel organic media, methylbenzyl naphthalene (MBN), was newly prepared on a large scale. For the storage and extraction of H₂, new Pt and Ru nanocatalysts were developed for hydrogenation and dehydrogenation, respectively, was developed. The MBN showed the lowest dehydrogenation enthalpy among homocyclic LOHC media, which allows facile dehydrogenation of the media. In addition, further works will also present the doping of sulfur elements on Pt on TiO₂ for efficient and selective dehydrogenation of MBN. Despite the fundamental understanding, the new materials may provide a unique opportunity for H₂ energy utilization.