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Australian crystals set to take over industry

Forty per cent of the energy consumed by industry is used to separate things—in natural gas production, mineral processing, food production, pollution control. The list is endless. Each offers an application for Matthew Hill’s crystals. He has demonstrated that the space inside metal–organic frameworks (MOFs)—the world’s most porous materials—can be used as an efficient and long-lasting filter.

By choosing different combinations of metals and plastics, Matthew’s CSIRO team can make a wide range of customised crystals. Then, using antimatter and synchrotron light, they map the internal pores, determine what each crystal can do, and explore potential applications.

First cab off the rank is natural gas separation. His team has developed a membrane embedded with crystals that efficiently separates natural gas from contaminants and lasts much longer than traditional membranes. He’s working with gas companies to develop the patented technology that could replace the multistorey processing plants found on gas fields with smaller truck-sized systems.

Patented applications for the food industry are also in the works. And further down the track are: carbon dioxide scrubbers; safe compact storage systems for gas and hydrogen; and even crystals that could deliver drugs or fertilisers on demand.

For his work on the development of metal–organic frameworks for practical industrial application, Dr Matthew Hill, Australian Research Council Future Fellow and leader of the Integrated Nanoporous Materials team at CSIRO, has been awarded the 2014 Malcolm McIntosh Prize for Physical Scientist of the Year.

MOFs—networks of metal atoms linked and separated by carbon-based (organic) compounds—were first synthesised in the late 1980s by chemist Professor Richard Robson at the University of Melbourne. About 10 times more porous than any material known previously, MOFs have a couple of other important properties of great value. They form as crystals, so their structure can be worked out precisely. And, because they can be made using a broad range of metals and organic compounds, a huge number of different structures with different characteristics can be constructed. So they can be designed to suit specific applications.

At the time when Robson made the first MOFs, Matthew Hill was in his teens in Sydney, totally unaware of them and the role they would play in his future. But he was already showing signs of the scientist he would become. “I think I was made this way,” he says.

By the time Matthew was four, his mother Kim had already found she could use mathematics as an inducement for good behaviour. “I was always interested in maths and science. She would write out sums for me to do—additions and subtractions—as a reward for not throwing tantrums,” Matthew says.

He was selected to go to the prestigious North Sydney Boys High, “where all the teachers were outstanding”. From there, Matthew went to do an advanced science degree in chemistry at the University of New South Wales—the first of his family to go to university in the 180 years they have been in Australia. He continued on to a PhD with Professor Rob Lamb, studying photonic films, making more than 300 new chemicals, and gaining an appreciation of materials and entrepreneurship in the process.

By that stage he had become convinced that if he was going to be a researcher in Australia, CSIRO was the place. “I liked the idea of using my science to help people, and CSIRO seemed to fit the bill of focusing on what was good for the country.” As luck would have it, he was hired by Dr Anita Hill, who was already famous for her work on porous materials. Together they worked out which materials they could explore to build on her successes in energy, water and the environment.

It turned out to be a no-brainer. “MOFs were the most promising of all. They had the most holes—the most space—with which to work, and they were the most varied in composition which meant they could be optimised for any application. Their use was limited only by our imaginations and our ability as chemists.”

So Matthew Hill set to work developing MOFs as a platform technology to enable the development of products for industries ranging from agriculture and water to energy and defence. First, he needed to be able to guarantee a dependable supply. “The first MOF I ever made was one gram for a test. But it couldn’t be mixed up in a single bowl. I had to combine the contents of 40 small separate containers.”

Matthew and collaborator Dr Tash Polyzos have since developed a continuous-flow production system, which involves a careful mixing of ingredients using piping of small diameter. The time of crystallisation has dropped from 24 hours to just over a minute, and they have now made 15 kg in a day. And Matthew says there’s no particular barrier to scaling up the process to commercial quantities.

Individual MOFs need to be analysed and tested for their structural and functional properties, their chemistry and pore size, their stability and purity. And that has been accomplished too. As crystals, the structure of MOFs can be measured precisely by means of X-ray crystallography using the Australian Synchrotron, near to the research group’s base on Monash University’s Clayton campus. Pore sizes and shapes are assessed using a technique involving antimatter, positron annihilation lifetime spectroscopy.

With the production and analysis providing a base, the applications have been innovative and wide-ranging. For instance, on a three-month visit to the University of Colorado in 2011, Matt and Professor Richard Noble began a study of whether the efficiency of the polymer membranes used as molecular sieves to separate gases could be improved by incorporating MOFs. What they found surprised them.

Not only did the membranes work three times better, they also lasted much longer. Most polymer membranes collapse after about three weeks, which rules them out of many industrial applications. But when the MOFs were added, they kept on working. “It turns out that the chemistry of the MOFs is attractive to polymers,” says Matt. “The polymer chains thread through the MOFs, and are propped apart by them. So they can’t collapse.” That observation is now well on the way to changing how gas mixtures are processed industrially.

On an earlier trip to the US in 2008, Matt went to work at the University of California, Berkeley. There he explored the risky idea of building MOFs using the light metal beryllium, which is highly reactive. The resulting MOF broke the world record for the storage of hydrogen at room temperature. That certainly attracted the attention of industry, particularly the auto industry. With further work, beryllium has now been replaced for industrial purposes by other metals that are cheaper and safer. And new MOFs have been developed that smashed the world record for storage of CO2.

“The energy-expensive part of carbon capture is in its release. So we teamed up with Monash and Sydney Universities to make a MOF that soaks up the CO2 part, and changes shape when concentrated sunlight shines on it. It wrings itself out like a sponge, and releases 70 per cent of the CO2 it has stored.”

Despite all these achievements, Matt believes his greatest contribution is his support of the next generation of scientists. “These days I act more as a coach for younger researchers. One of my mottos is ‘Always try to hire people who are smarter than yourself’.”

The result is a laboratory which is diverse in terms of disciplines, and so can address any issue or application from a variety of perspectives. “This sets us apart from traditional fundamental research,” he says. And it looks to be the beginning of something very productive for Australia and the world.

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