Opinion

Conference Catch Up

PhD student Edwin Clatworthy explores the latest chemistry being done around the world.

This year I was fortunate enough to attend my first international conferences to present some of our group’s latest research. Not only did I get to hear and see some of the latest chemistry being done around the world, but also get a chance to meet many experienced chemists and gain a lot of knowledge.

In the first week of July the 42nd International Conference on Coordination Chemistry (ICCC) was held in Brest, France. The ICCC is one of the longest running chemistry conferences spanning a broad and diverse range of areas including bio-inorganics and medicine, organometallics, materials and nano-chemistry, self-assembly and supramolecular structures, catalysis, and sustainability. The conference ran for five days with over 603 speakers including two Nobel laureates, Jean Marie-Lehn and Richard Schrock. Two weeks after the ICCC, the 27th International Conference of Organometallic Chemistry (ICOMC) was hosted in Melbourne. Like the ICCC, the ICOMC had several hundred delegates and covers a broad range of topics but with a greater focus on metal complexes.

My presentations at both the ICCC and the ICOMC contained a combination of work I had done during my honours year and first year of my PhD. This included collaborative work with another honours student, Julia Picone-Murray, and postdoctoral researcher Dr Xiaobo Li. Being able to present at these conferences was very fulfilling, but also terrifying, because you are showing the world your research and how it fits into the broader chemistry knowledge, as well as receiving feedback and advice from experts in the field.

We have long been interested in cobalt acetate, which is a salt of the metal cobalt, as it is a well-known industrial oxidation catalyst. Oxidation reactions typically involve the addition of oxygen to an atom or molecule to generate a new product. Currently, the petrochemical industry utilises cobalt acetate-based catalysts for the conversion of aromatic molecules obtained from crude oil to more valuable products. Aromatic molecules are the molecular building blocks for a variety of modern day materials and products such as plastics, coatings, resins, pharmaceuticals, food additives, packaging, and detergents.

Crude oil
Aromatic molecules from crude oil, benzene, toluene, ethyl benzene and xylene.       

Our research focussed on applying cobalt acetate catalysts to convert biomass, such as lignin, into potentially useful chemical products. The application of cobalt acetate catalysts to lignin conversion is important because as an established catalyst process many of the developmental issues such as corrosion and recycling of the cobalt catalyst have been solved. Lignin is the largest renewable source of aromatic molecules, accounting for 15 – 30% by weight and 40% by energy of biomass. However, it is a complex polymer composed of many different sub-units and its structure is quite complex compared to the mixture of aromatic molecules found in crude oil. As lignin is extracted and processed from biomass, such as during paper production, the polymer structure begins to break down into smaller molecules creating a complex mixture of different compounds.

Our investigation involved targeting lignin fragments of various sizes and composition to understand how each would behave in the cobalt-acetate catalyst system. We found that each of the fragments tested could be oxidised, but would yield different product mixtures depending on the fragment size and structure. Smaller fragments were more likely to undergo polymerisation reactions to form undesirable products, but the majority of substrates we tested could be converted into useful chemicals with high selectivity. This means that cobalt acetate catalysts are robust enough to process mixtures of lignin fragments, such as the lignin waste from pulp mills. To develop this technology further, the next improvement could make use of flow systems that would recycle unreacted lignin fragments. A flow system can allow products to be separated from the reaction mixture while recycling any unconverted material back into the reactor, improving the total conversion and yield.

lignin
Idealised structure of lignin. As the structure breaks down a complex mixture of different fragments is formed.

Apart from applications in biomass conversion, cobalt acetate complexes have also been of great interest recently for water splitting applications. Water splitting is an attractive reaction to exploit because we can use the hydrogen as a transport fuel and to provide electricity which is a green and renewable source of energy. However, in addition to hydrogen, oxygen will also be generated during the water splitting process. For overall water splitting to occur efficiently, the evolution of hydrogen and oxygen needs to occur at similar rates. Finding catalysts that can perform the evolution of oxygen from water is arguably more challenging than the evolution of hydrogen because from an energy point of view it is more demanding.
Nature achieved the evolution of oxygen, necessary for the development of complex life, over billions of years in plants. This is facilitated by using a cuboidal cluster of manganese, calcium and oxygen atoms held together in a giant protein complex called Photosystem II. Chemists have spent decades trying to develop synthetic analogues of the cluster in Photosystem II which has proven to be one of the greatest challenges in chemistry. Due to the structural similarity of the cobalt acetate cubane Co43-O)4(µ-OAc)4(py)4 to the cluster in Photosystem II it has received a lot of attention as a potential oxygen evolution catalyst. The application of cobalt acetate for oxygen evolution is part of my existing research which I hope to report back on soon.

photosystem
Mn4CaO5 cluster in Photosystem II (Umena et al. Nature, 2011, 473, 55-60)

Overall, the ICCC and ICOMC were great opportunities to meet both international and local researchers of various specialities. The conference environment allows many chemists, working in similar fields, an opportunity to directly share their latest insights and develop collaborations. For me personally, having a chance to speak to many Australian researchers meant I could build connections with local experts and specialists.

Developing collaborations between various institutions allows researchers and students to perform critical experiments using equipment and techniques we normally may not have access to. My upcoming experiments on the cobalt cubane and other projects will all involve collaborations with other institutions, the results of which I hope to share with you soon. Until next time!