Clean water with crystals

Dr Cara Doherty, materials scientist, CSIRO, Melbourne

Dr Cara Doherty (credit: L’Oréal Australia)Cara Doherty is developing new technologies that could transform water filters, batteries and medical sensors, and clean up carbon emissions. And it all comes down to holes and surface area.

She has a vision for a new manufacturing industry for Australia. She works with crystals that are packed with… nothing. They’re highly porous sponges—down to a molecular level—and can be customised to absorb almost any molecule.

These crystals are metal–organic frameworks (MOFs). They can be challenging to make. And it’s also difficult to determine which crystal will be good for which job. But it’s even harder to deploy the crystals—to put them in the right place to do useful work.

Cara uses antimatter (positrons) and synchrotron light (X-rays) to measure the crystals and their properties. Then she uses her patented technique to imprint useful shapes for devices.

With the help of her L’Oréal For Women in Science Fellowship she will investigate how to take the next step: to develop the 3D structures that would be needed for a smart water filter.

About 780 million people worldwide, according to the United Nations, have no clean water—more if you count those whose access has temporarily been interrupted by disasters such as floods, earthquakes or tsunamis.

Cara is an Australian Research Council (ARC) Discovery Early Career Research Award (DECRA) Fellow working in the CSIRO’s Manufacturing Flagship in Clayton. She thinks that MOFs are the key to smarter, lighter water filters.

Metal–organic frameworks are crystalline compounds in which clusters of metal atoms are linked by carbon-based groups. They are highly porous, and the huge expanse of surface area means that, as a filter, they have a greater chance of interacting with the pollutants in waste water.

Because the properties of MOFs can be changed by varying the types of metals or the groups between them, they can be carefully tailored to their task. Cara is proposing to employ them as molecular traps to pull chemical and biological pollutants out of non-potable water. But MOFs can also potentially be useful for detecting or diagnosing disease, soaking up greenhouse gases, or storing methane and other fuels. What’s more, MOFs can incorporate light-emitting molecules, such as quantum dots, that can indicate whether they are doing their job or when they need to be cleaned.

Although chemists are busy designing and creating new and clever MOFs, few have been incorporated into practical applications yet. The reason is that, in order to be useful, they need to be durable and to be carefully deployed in the right form in the right places. And that’s where Cara comes in.

She hopes that by developing techniques to build three-dimensional structures out of stable MOFs, she will be well on the way to fashioning cheap, reliable and efficient filters to clean up contaminated water. Her $25,000 L’Oréal Australia and New Zealand For Women in Science Fellowship should give her a good start.

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In a way, Cara has been moving towards this project for most of her life—she just didn’t know it. It all began in secondary school in Perth when she had no idea what she wanted to do beyond something in science. So she enrolled in a science degree at Curtin University and ended up doing physics for the first time.

Her physics-based degree then found her something else—a job in a start-up company that was developing a structural monitoring system to detect cracks in aircraft. For two and a half years, she worked in a practical commercial environment which was research-based. And she discovered that if she wanted to develop her own interesting projects she would need a PhD.

So Cara ended up at CSIRO undertaking a PhD at The University of Melbourne. Her research was to do with constructing high-powered electrodes for lithium-ion batteries—the rechargeable batteries now common in consumer electronics, from computers to electric cars. Her studies led to her learning about many of the concepts she will bring to bear on developing her MOF water filters.

The electrodes were built with pores to allow the largest possible contact with battery fluids. The materials out of which they were fabricated were hierarchical. That is, they included three-dimensional pores of different scales—large pores for easy access and movement of fluid lined with much smaller pores for intimate molecular interactions.

As a postdoctoral fellow, Cara went on to work full time at CSIRO in a team led by Dr Anita Hill, and she has continued to research porous materials with Dr Paolo Falcaro. Among other things, she has become an expert at using positron annihilation lifetime spectroscopy (PALS)—a clever technique which employs radioactive sources emitting positrons (antimatter) to measure pore sizes in nano-structured materials. She also uses synchrotron light in Australia and Italy to explore the structure of porous materials.

Until recently, the conventional techniques used to make the majority of MOFs involved nasty conditions such as high temperatures and pressures, and harsh chemicals such as dimethylformamide (DMF), making the MOFs difficult to handle and deploy. Cara invented and patented a process that allows preformed MOFs to be deposited on surfaces in predetermined patterns under much more benign conditions. Separating the patterning process from the synthetic process makes this versatile technique suitable for most MOFs. It is a combination of photolithography, the technique used to print intricate circuits on silicon chips, and an imprinting technique.

All these strands—her experience with three-dimensional and hierarchical materials, with deposition using photolithography and other techniques, and her familiarity with PALS and synchrotron analysis—will come together in trying to build the MOF-based water filter. The project also parallels her DECRA project of trying to generate biologically active devices for use in medicine.

The trickiest problem, Cara says, lies in determining the best way to build the structures she wants in three dimensions. But her past work has provided her with several ideas and techniques to try. One method she will employ is to build a three-dimensional metal scaffold and then form the MOF in situ, drawing on the metal atoms from the scaffold. An alternative technique involves electrochemistry for MOF deposition.

MOFs and porous materials in general are not only of interest in Australia. Cara’s work at CSIRO has taken her to Italy, Japan and Korea and led to close collaboration with research groups in those countries.

“Within a decade, I would like to see MOFs being commercialised and used in devices. I think there are really big opportunities to develop smart, intelligent materials with multiple functions that can detect or trigger molecular interactions.”

Read the latest news about Dr Cara Doherty


2009PhD (physical chemistry), The University of Melbourne/CSIRO Molecular and Health Technologies, Melbourne
2002Honours (physics), Curtin University of Technology, Perth
1999Bachelor of Multidisciplinary Science (physics), Curtin University of Technology, Perth

Career highlights, awards, fellowships, grants

2014–2016ARC Discovery Early Career Researcher Award (DECRA) Fellow, 3D hierarchically porous structures from metal–organic frameworks (MOFs) for investigation of their structural, spatial and chemical performance as biomolecular scaffolds for use in next generation sensing devices and biomedical implants, CSIRO Manufacturing Flagship, Melbourne
2014Contributing Investigator, Magnetic framework composites as chemical and biological contaminant scavengers for the treatment of surface, sea and groundwater, Intelligent Processing Transformational Capability Platform for an IASTE student
2013­–2014Principal Investigator, Converting metals into intelligent ultra-porous metal–organic frameworks-based filters, Intelligent Processing Transformational Capability Platform for a Proof of Concept study
2013Victorian Young Tall Poppy Science Award, Australian Institute of Policy and Science
2012­–2014Contributing Investigator, Monitoring and prediction of catastrophic multi-sloped screen failures, The Australian Coal
2012–2013Contributing Investigator, CSIRO Office of the Chief Executive Postdoctoral Fellowship, Patterning biological activity in porous materials
2012The Theo Murphy High Flyers Think Tank 2012 Award, Australia’s Population: Shaping a Vision for our Future, Adelaide
2012Invited presentation, Nanostructured mesoporous materials for bio-encapsulation and device fabrication, International Conference on BioNano Innovation, Brisbane
2012Invited presentation, Combining metal–organic frameworks with functional micro- and nano- particles, Centre for Imaging Technology Commercialization—4th International Conference Smart Materials, Structures and Systems, Montecatini, Italy
2011Australian Academy of Science Australia–Korea Early Career S&T Researchers Program Award to travel to South Korean Laboratories
2010–2011Contributing Investigator, Office of the Chief Executive Postdoctoral fellowship CSIRO, Thermally rearranged polymer membranes: tailoring porosity for separation
2009–2014CSIRO Science Leader Postdoctoral Fellow, Advanced functional porous materials for energy, water and the environment, CSIRO Materials Science and Engineering
2007Postgraduate Overseas Research Experience Scholarship, 3 months in Max Plank Institute, Department of Colloids and Interfaces, Golm, Germany. From The University of Melbourne

Top five publications

Doherty CM, Grenci G, Riccò R, Mardel JI, Reboul J, Furukawa S, Kitagawa S, Hill AJ and Falcaro P (2013) Combining UV Lithography and an Imprinting Technique for Patterning Metal–Organic Frameworks, Advanced Materials 25: 4701–4705. (Impact factor 15.409, 5 citations)

Doherty CM, Buso D, Hill AJ, Furukawa S, Kitagawa S and Falcaro P (2014) Using Functional Nano- and Microparticles for the Preparation of Metal–Organic Framework Composites with Novel Properties, Accounts ofChemical Research 47: 396–405. (Impact factor 24.348, 3 citations)

Falcaro P, Ricco R, Doherty CM, Liang K, Hill AJ and Styles MJ (2014) MOF positioning technology and device fabrication, Chemical Society Reviews DOI: 10.1039/C4CS00089G. (Impact factor 30.425, 0 citations)

Doherty CM, Caruso RA, Smarsly B, Adelhelm P and Drummond CJ (2009) Hierarchically Porous Monolithic LiFePO4/Carbon Composite Electrode Materials for High Power Lithium Ion Batteries, Chemistry of Materials 21: 5300–5306. (Impact factor 8.535, 103 citations)

Doherty CM, Caruso RA, Smarsly B and Drummond CJ (2009) Colloidal Crystal Templating to Produce Hierarchically Porous LiFePO4 Electrode Materials for High Power Lithium Ion Batteries, Chemistry of Materials 21: 2895–2903. (Impact factor 8.535, 93 citations)


Dr Cara Doherty (credit: L’Oréal Australia)
Dr Cara Doherty (credit: L’Oréal Australia)
Dr Cara Doherty (credit: L’Oréal Australia)
Dr Cara Doherty (credit: L’Oréal Australia)
Dr Cara Doherty (credit: L’Oréal Australia)
Dr Cara Doherty (credit: L’Oréal Australia)