Turning sugars into platform chemicals with Earth-abundant catalysts
Catalysis and Sustainable Chemistry Community
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by Yang Liu and Enrico Della Gaspera
The impact of anthropogenic carbon dioxide on climate change, coupled with the growing demand for sustainable resources driven by a rapidly increasing global population, underscores the urgent need to transition the chemical industry to renewable carbon sources. Biorefineries present a highly promising solution for sustainable chemical manufacturing, wherein waste biomass or plastics are transformed into energy vectors, such as liquid hydrocarbons and hydrogen (H2), as well as chemical building blocks.
One such chemical building block is 5-(hydroxymethyl)furfural (HMF), which can be synthesised from biomass and subsequently transformed into fuel precursors, solvents, and value-added chemicals. HMF can be produced from glucose (from cellulose biomass) through a chemical cascade involving isomerisation to fructose followed by dehydration, promoted by Lewis and Brønsted acid catalysts, respectively.
Zirconia (ZrO2) finds widespread application in catalysis due to its amphoteric surface chemistry, tunable crystalline phases and oxygen vacancies, and hydrothermal stability. These properties make zirconia an attractive catalytic material for the aqueous phase conversion of glucose to HMF.
A recent study led by Griffith University ( Adam Lee , Karen Wilson ) in collaboration with RMIT University ( Yang Liu , Enrico Della Gaspera ), The University of Manchester (Luke Forster, Aristarchos Mavridis ), University of Technology Sydney ( Andrea Merenda ), The University of Queensland ( Muxina Konarova , Mohamed Ahmed) and CSIRO (Aaron Seeber) investigated the influence of zirconia phase on glucose (and fructose) conversion.
Lewis acidic, monoclinic zirconia (m-ZrO2) nanoparticles preferentially promotes glucose isomerisation, but is unable to dehydrate fructose to HMF, whereas the tetragonal phase (t-ZrO2) possesses Brønsted acid sites conducive to fructose dehydration to HMF. Synergy between these zirconia phases can drive the chemical cascade in batch and continuous flow reactors. In continuous flow, a physical mixture of 15% m-ZrO2 : 85% t-ZrO2 increases HMF production six-fold compared to pure t-ZrO2, and obviates the need for subsequent catalyst/product separation.
Lewis acid sites at undercoordinated Zr4+ sites (blue circles) on m-ZrO2 surfaces promote glucose isomerisation to fructose, while Brønsted acid sites formed by polarisation of bridging hydroxyls (orange circles) with water chemisorbed at undercoordinated Zr4+ sites promote fructose dehydration to 5-HMF.
Meet the corresponding author:
Describe the broad area you work in:
My work sits at the intersection between chemistry and materials engineering. My team develops liquid-based syntheses for a variety of inorganic nanomaterials, mostly earth-abundant oxide semiconductors, either as thin-film coatings or as suspensions of colloidal nanoparticles. We target applications in the energy space, such as smart (heat reflecting) windows, solar water splitting, catalysis, and various optoelectronic devices including solar cells, photodetectors, and electrochromics.
Why is your work important?
Many of the devices mentioned above rely on either expensive and scarce materials, or on costly and slow fabrication methods, and sometimes both. The ability to replace these rare materials with new ones composed of widely available elements, and the ability to deposit these active materials from liquid precursors using common techniques such as spraying and printing, can be a game changer in various energy technologies, provided that the performance in these devices is not compromised. My research aims specifically at developing new materials and/or processes to enable to achieve cheaper, greener and more efficient energy devices.
What moment stands out to you in your career?
There are many moments that stand out when I look back, but if I have to pick one, I would say the graduation of my first PhD student at RMIT. We built the lab together, went through countless long days of troubleshooting issues with equipment, and he still managed to get a mountain of excellent data for his thesis, which was accepted without any amendments. On a more personal level, the fact that my 6 year-old daughter wants to become a scientist and keeps asking to do experiments together (did anyone say elephant toothpaste?) is definitely one of my proudest moments.
If you could leave one mark on the [chemistry/engineering] profession, what would it be?
There are so many unsolved challenges that disciplines such as chemistry, engineering, materials science and nanotechnology can address, from water purification to clean energy, from fighting antimicrobial resistance to food availability, and many, many more. If I had to pick one close to my area of research, it would be developing alternative, greener, and more efficient methods to harvest and store solar energy.
What do you enjoy doing outside the [chemistry/engineering] field?
Spending as much time as possible with my wife and daughter, playing basketball, cooking, and travelling back to Europe during the Australian winter to see my Italian family and friends.
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