Scientists hope to help asthma sufferers and others needing oxygen at home by developing ‘molecular sponges’ with nanoscale-sized pores to purify the air.

There’s possibly nothing more frightening than struggling to take a breath. Something asthmatics and others with respiratory diseases know all too well.

Many of these people depend on portable oxygen concentrators, small machines that concentrate oxygen out of air. But there are limitations on the portability and longevity of these devices.

New technology allowing small, lightweight, more efficient and affordable oxygen concentrators could underpin a new generation of portable oxygen devices used in hospitals and in people’s homes. And it turns out that the fastest growing class of materials in chemistry, metal-organic frameworks (MOFs), may be able to make this happen.

A MacDiarmid team of researchers is looking at using MOFs to enrich oxygen from air, as Massey professor and MacDiarmid researcher Shane Telfer explains.

“MOFs are mostly free space, like an open porous net, with a metal at the corners and an organic component as the rods or linkers.”

To understand how MOFs work, Telfer says, you need look no further than your kitchen sponge. “The pores in your kitchen sponge are the same size as a water droplet. That’s why your sponge works. The pores in metal organic frameworks (MOFs) can be made the same size as gas molecules. That’s how they can absorb O2.

“One of our MacDiarmid PhD students has run calculations to show that if you pass air through a MOF you can capture the oxygen. So now we are trying to replicate this experimentally to find a MOF that is more efficient, cheaper and has a longer lifespan than the current oxygen generation technology. Ideally, it’ll also be resistant to other components in the air such as water vapour. We’d be able to patent a material like that.”

Researchers worldwide are finding these three-dimensional ‘molecular sponges’, with pores on the nanoscale (about the size of molecules), rather useful across a range of areas.

One of these is climate change remediation. Absorbing CO2 is high on the priority list right now, with many companies (such as Mosaic Materials, a start up based in Berkeley, California) seeking to commercialise MOFs to absorb CO2, from smoke stack emissions to prevent global warming. MOFs can also store other gases, such as hydrogen and methane, for fuel.

The MacDiarmid team, which pulls together researchers from all over New Zealand, includes Professor Paul Kruger from the University of Canterbury, who is looking into precisely this area – how MOFs can store gases for fuel or capture CO2 from emission streams – and Dr Carla Meledandri from Otago University, who is investigating new and more efficient ways to make known MOFs.

Telfer says MOFs are useful for more than just gas capture. “MOFs could also deliver a drug to a specific site within the body.”

MOFs evolved from research carried out in Australia 30 years ago and significant advances in their design, synthesis and applications were made in the early 2000s by US chemist Omar Yaghi. Already over 6000 new MOF structures are published each year, and many of these are collecting patents.

Patents interest the team of MacDiarmid researchers too, although Telfer points out that much of the research is at an early stage. “Like much of materials science, most current MOF research is focused on pushing back the boundaries of fundamental knowledge.”

Yet MOFs are soon to be used commercially in New Zealand, with a new technology to slow fruit-ripening licensed for use here by Irish company MOF Technologies.

Telfer says the potential applications from MOFs would fit well with the manufacturing landscape in New Zealand.

“We’re are looking to work with New Zealand companies to develop new MOFs for various gas storage and separation applications. The translation of our research towards commercialisation was boosted by the funding we – as a team of NZ scientists – recently received from MBIE to work with our industry-facing collaborators at CSIRO [Commonwealth Scientific and Industrial Research Organisation] in Melbourne.”

Another trick MOFs have up their (porous, three dimensional, nanoscale) sleeves is being able to mimic biological molecules, like enzymes.

“Just as an enzyme makes biological reactions work better, MOFs can be engineered to do the same for industrial processes. Enzymes have a cavity or pocket where the amino acids are oriented in order to capture a chemical and help it transform. MOFs can be designed with a similar pocket, and by altering the chemical environment in the pore, we are inventing new MOFs that could pave the way for greener industrial processes, like making pharmaceuticals.”

The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.