A circular future for gas storage materials: the Metal-Organic Frameworks (MOFs) developed in MAST3RBoost

The Metal-Organic Frameworks, first discovered in the 1990s, have gained a lot of attention in recent years thanks to their many innovative applications across different fields. But what exactly are these materials, and why are they so interesting?

What are MOFs and why are they at the heart of today’s technological revolution?

 Despite their complex name, understanding what a MOF is can be surprisingly intuitive. MOFs are porous structures made of metal ions or metal clusters connected by organic molecules, called ligands. You can picture them like a construction set: with just a few basic pieces you can build a repeating module, and by joining those modules in every direction you get a three-dimensional structure full of channels and cavities capable of trapping other molecules.

MOFs offer to big advantages over other porous materials like zeolites or natural clays:

• They are highly versatile. MOFs can be designed almost tailor-made choosing both, the metal and the organic ligand. This flexibility allows researchers to create thousands of different structures. For example, the Cambridge Structural Database listed 108,063 MOF structures as of November 2025.
• They have a very large internal surface area. Some MOFs reach up to 7,000 m² per gram. That means that just one gram of material has a surface area equivalent to an entire football field.

Because they can be tailored to host molecules of specific sizes and because of their huge internal surface area, MOFs are extremely promising for applications such as gas purification and storage, drug delivery, catalysis, and even next-generation sensors and batteries.

Why has MAST3RBoost focused on iron-based MOFs?

As mentioned above, MOFs can be built using many different metals (copper, cobalt, titanium…). However, MAST3RBoost has placed special emphasis on iron-based MOFs. The reason is simple: iron offers unique properties and remarkable chemical versatility.

Iron is one of the most abundant and accessibility elements. This makes it more attractive than other metals that are more expensive, less abundant, or present environmental concerns during extraction or disposal.

Fe-MOFs also tend to have low toxicity compared to those based on heavy metals. They show excellent chemical stability and strong biocompatibility, which makes them suitable for biomedical uses. And while some porous materials, like zeolites, are not very stable in organic solvents, Fe-MOFs perform very well under these conditions.

Certain Fe-MOFs, such as MIL-53(Fe), are even flexible: their structure can expand or contract depending on the molecule entering the pores, a property known as breathing. This feature can improve the selective capture of specific gases.

For a more detailed and technical overview, you can refer to Recent advances in Fe-based metal-organic frameworks: Structural features, synthetic strategies and applications, published within the MAST3RBoost project.

How are MOFs made? A revolution in synthesis methods

Early MOFs were produced using thermal methods that required long reaction times and were not very environmentally friendly. In recent years, however, cleaner and more efficient approaches have been developed.

Microwave-assisted synthesis, for example, provides rapid and direct heating, dramatically reducing reaction times. Another promising technique is the use of ultrasound. Sonication creates tiny bubbles that collapse and generate extreme local temperatures and pressures, speeding up chemical reactions.

In the paper Synthesis of iron-based metal–organic frameworks and carbon derivatives via unconventional synthetic methods and waste precursors with potential for gas storage, project partners tested these unconventional routes. They achieved homogeneous and well-defined structures with lower energy consumption.

One of the most striking results from this review is the use of waste streams as feedstock. K. Mosupi et al. (2025) used recycled PET as a ligand source and acidic mine drainage as the iron source.

Their work shows that MOFs can be synthesized from waste materials, reducing costs and environmental impact. It is a clear example of how circular economy principles can be applied to advanced materials.

From MOF to carbon: a transformation with energy applications

A particularly interesting aspect of recent work on Fe-MOFs is their conversion into carbon-based materials, known as MOF-derived carbons (MDCs). Producing these MDCs is simple: MOFs are heated in an inert atmosphere, without oxygen, so the organic part carbonizes while the metal component can later be removed.

The resulting material is a porous carbon with a highly ordered microstructure and greater thermal and chemical stability than the original MOFs. These materials are promising for use in harsher environments and are especially effective at adsorbing smaller gases.

Looking ahead: a circular approach to gas storage

MAST3RBoost has played a key role in advancing the study of Fe-MOFs and has shown that both MOFs and MOF-derived carbons can be produced through cleaner processes using waste as a raw material.

For CO₂ capture, Fe-MOFs are particularly promising. Their flexible structure and the breathing behavior allow the pores to adapt to CO₂ molecules, improving selectivity and adsorption capacity. MDCs also show strong affinity for CO₂, and studies suggest that adjusting carbonization temperatures helps fine-tune micropore distribution and boost performance.

Hydrogen storage, however, remains more demanding. Because H₂ molecules are so small, materials must have extremely narrow micropores and very specific adsorption energies. Current commercial materials still perform better, but the results obtained so far open the door to developing circular, iron-based materials that can be optimized specifically for hydrogen.

Overall, MAST3RBoost has established a full circular value chain: from fast, energy-efficient synthesis of MOFs using plastic and mining waste, to transforming those MOFs into functional carbon materials with real environmental applications. This integrated approach shows that cleaner, scalable, and circular technologies for gas capture and storage are possible.

Author: Noemi Alonso