Metal Organic Frameworks (MOFs): An Advanced Material That's Finally Coming of Age for Nanoscale Commercialisation
The commercialisation levels and potential of nanomaterials has often been misjudged over the years—at both ends of the scale.
On one hand you had carbon nanotubes (CNTs) that was promising to be one of the best things ever, but fizzled out very quickly when end users couldn’t find a way to effectively work them into their products.
On the other hand, you have metal organic frameworks (MOFs), which have hardly been publicised compared to other advanced materials, and even when they’re mentioned, there are often discussions about how they are a small-scale production material—which is certainly not the case today.
So, what are MOFs? MOFs are class of hybrid porous materials that contain a mixture of organic linkers and inorganic metal ions. MOFs have pores that run throughout the length of the material and are used to separate out materials in a mixture or capture materials in their pores.
There are a number of different MOFs in existence and are the synthetic answer to zeolites (which are naturally occurring but have a similar porous network). MOFs are manufactured with defined pore sizes, pore charges, and internal functional groups so that they can selectively filter or trap molecules of interest in a heterogenous mixture.
Lots of people still believe that MOFs are produced on a small scale, but this is not the case and hasn’t been for some time. Through my discussions with multiple companies in the field over the years (and as recently as a couple of months ago), there are still many people who don’t consider MOFs as a viable option due to (wrongly) thinking that there is not going to be enough material volume to fulfil their needs.
This could not be further from the truth. In fact, different MOFs can be manufactured at the multi-tonne level each year and represent a real opportunity to solve a number of challenges. It is an advanced material that now has robust manufacturing operations in place and can easily meet the demands of the different industries.
So, while there has been a hesitancy to use MOFs based on their ill-informed production levels, recent discussions that I had with multiple MOF companies at the Advanced Material Show this year seem to suggest that this landscape is changing—and end users are becoming more wise to the production volumes possible with today’s MOF manufacturing technologies.
So, now that MOFs are finally starting to gain some level of commercial validity in the wider industry, let’s look at a few key application areas where MOFs are already having an impact and are likely to penetrate much further in the coming years.
Carbon Capture
When MOFs are discussed, carbon capture is often brought up because the pores of the MOF can be specially designed to remove carbon (in the form of carbon dioxide) from our atmosphere. There are already a couple of well-established companies working in this area.
The first of these is the UK-based company, Promethean Particles. While Promethean Particles are also developing MOFs for energy storage (fuel cells and batteries) and hydrogen storage applications, the main area where they are developing MOFs for is carbon capture—in both direct air capture and post-combustion air capture scenarios.
These MOFs at Promethean Particles have been specifically developed to capture carbon dioxide (MOFs for other applications are tailored in other ways). In direct air capture applications, the carbon dioxide molecules are removed from the general atmosphere. For post-combustion applications (where there is the most carbon content), the MOFs remove the carbon dioxide from the flue gas streams in power plants.
Promethean Particles have huge reactors for making MOFs and can produce MOFs on a scale of 1000 tonnes per annum. Production levels on this scale highlights the real large-scale potential for MOFs and really shows how it is not just a lab-based or pilot-scale material anymore. It’s a material that is here in large quantities.
Another UK-based company in the carbon capture space is Nuada. Originally a MOF manufacturing company called MOF Technologies, the company shifted focus from creating MOFs and being a supplier for different applications, to focusing on developing complete carbon capture systems using their MOFs.
Unlike the supplier side, they are not focusing on the potential for large scale volume but are highlighting the potential for MOFs by using them in a complete system that’s now on the market. Nuada are another company that are targeting post-processing/combustion carbon dioxide by attaching their capture system directly into the flue of industrial plants in the steel, cement, and power industries.
Once installed, these systems re-route the flue gas through a MOF carbon capture filter to selectively remove the carbon dioxide from the gas stream. The saturated filters are then regenerated using a vacuum to release the captured carbon dioxide gas into a high purity stream so that it can be recovered downstream and used in other industrial applications.
Water Harvesting/Filtration Applications
While carbon capture might the biggest area of potential for MOFs, there is also commercial developments in the water harvesting and filtration space. This time, the commercial advancements are coming from novoMOF in Switzerland.
novoMOF are also involved with carbon capture, biogas upgrading, and gas purification applications, but when I spoke to them recently, they stated that harvesting water from arid environments was a key application focus for the company.
MOFs are now being used to harvest atmospheric water in desert conditions and don’t require an energy system to desorb the water once collected. The water is absorbed into the MOF during the cold nights, and the sunlight desorbs the water during the day so that it can be collected.
MOFs could open up new ways of collecting water in harsh environments, as the tests so far have shown great results in arid climates where water is traditionally scarcer.
Written by Liam Critchley
