The new magnets that will revolutionize technology
Imagine a material so light it would float like the finest feather, yet with the ability to act as a powerful magnet at room temperature. Now go one step further: think that this material has thousands of tiny holes, like a nanometric Swiss cheese, capable of storing gases or even distinguishing between similar molecules like oxygen and nitrogen simply by their magnetic behavior. This is not science fiction, but the fascinating world of magnetic nanoporous materials, a research field that is about to revolutionize everything from energy storage to future computing.
On the other hand, high-spin molecules are those in which electrons present a high intrinsic angular momentum (spin), giving them unique magnetic properties. The combination of these two concepts opens a field with almost magical possibilities.
Nanoporous materials are like buildings with multiple empty rooms on a nanometric scale. Some, like zeolites or metal-organic frameworks (MOFs), have crystalline structures with perfectly defined pores . Others, like activated carbon, present a more disordered network of cavities 1 .
The true magic of these materials lies in their high specific surface area: a single teaspoon of some of them can have the surface area of a football field. This characteristic makes them ideal for applications such as gas adsorption, catalysis or energy storage 1 .
Each electron is like a small magnet spinning on itself, a phenomenon physicists call spin. In high-spin molecules, these electrons do not pair their orientations, but align in the same direction, creating a strong molecular magnetic moment.
Magnetic materials are classified according to how these spins align:
The real revolution comes when we combine the properties of nanoporous materials with those of high-spin molecules. Imagine a crystalline sponge that is also a good magnet.
Until recently, these materials only exhibited magnetism at cryogenic temperatures, but recent research has discovered compounds that maintain their magnetic ordering above room temperature. A notable example is V(TCNE)₂, a material that is both magnetic and microporous at room temperature 5 .
These materials are not only magnetic, but their porous structure allows hosting guest molecules, which can modify their magnetic properties. This is called "adaptive magnetism" or "chameleonic magnetic materials".
In 2018, a research team performed an extraordinary experiment with a material called [{Ru₂(3,5-F₂PhCO₂)₄}₂{TCNQ(MeO)₂}] 2 . This compound acts as a magnetic gas discriminator, capable of distinguishing between oxygen (paramagnetic) and nitrogen (diamagnetic) despite their similar size and physical properties.
The results were revealing: when the material absorbed N₂ or CO₂ (diamagnetic gases), it behaved as a ferrimagnet with an increasing Curie temperature (T_C). In contrast, when it absorbed O₂ (paramagnetic), the material continuously changed from a ferrimagnet to an antiferromagnet depending on the oxygen pressure 2 .
Even more surprising: when an external magnetic field was applied to the oxygen-saturated material, a new ferrimagnetic phase was obtained with the oxygen spins aligned synergistically 2 . This "chameleonic" material represents the first example of a magnet that can change its behavior to discriminate between similar gases like N₂ and O₂.
| Gas | Temperature (K) | Gate Opening Pressure (kPa) | Amount Adsorbed at 99 kPa (mL/g) |
|---|---|---|---|
| N₂ | 120 | 3.2 | 27 |
| CO₂ | 195 | Low (sudden increase) | 102 |
| O₂ | 90 | 0.1 (1st) and 36 (2nd) | 110 |
| O₂ | 120 | 3.1 | 64 |
| Material | Characteristic Temperature T* (K) | Langmuir Surface Area (m²/g) | Magnetic Behavior |
|---|---|---|---|
| V(TCNE)₂·0.95CH₂Cl₂ | 646 | Not determined | Ferrimagnet |
| V(TCNE)₂ (activated) | 590 | 850 | Ferrimagnet |
| V(TCNE)₂ + H₂ | 583 | - | Ferrimagnet |
| V(TCNE)₂ + CO₂ | 596 | - | Ferrimagnet |
| V(TCNE)₂ + ethylene | 459 | - | Ferrimagnet |
| Category | Pore Size | Common Examples | Typical Applications |
|---|---|---|---|
| Microporous | ≤ 2 nm | Zeolites, activated carbon | Gas adsorption, separations |
| Mesoporous | 2-50 nm | Mesoporous silicas | Catalysis, drug delivery |
| Macroporous | > 50 nm | Porous ceramics, foams | Filtration, catalytic supports |
Research on magnetic nanoporous materials requires specialized tools and reagents:
High-temperature furnaces for the synthesis of crystalline materials, such as those used to create NiI₂ single crystals for p-wave magnetism studies 3 .
Instruments such as the IGA-001 that accurately measure gas adsorption by determining mass changes .
Coupled to adsorption systems, such as those from Hiden Analytical, to analyze the composition of gas mixtures .
Equipment capable of generating high magnetic fields for the characterization of magnetic properties.
Such as V(CO)₆, used in the synthesis of V(TCNE)₂, which requires careful handling due to its sensitivity to light, air and heat 5 .
Various specialized instruments for material characterization, synthesis, and analysis of magnetic properties.
These materials have immense potential in emerging technologies:
In the field of spin electronics or "spintronics", materials like NiI₂ that present the new p-wave magnetism could allow creating computer memories that are faster, denser and less energy consuming 3 . MIT researchers have demonstrated that in these materials the electron spin can be switched by applying small electric fields, an advance that could save "five orders of magnitude" of energy compared to current technologies 3 .
Materials like [{Ru₂(3,5-F₂PhCO₂)₄}₂{TCNQ(MeO)₂}] could enable ultra-sensitive magnetic sensors for oxygen detection or the separation of atmospheric gases 2 .
Magnetic nanoporous materials could serve as a platform for the study of coupling between magnons (spin waves) and molecular spins, enabling new forms of quantum information transduction 5 .
The high surface area and magnetic properties of these materials make them promising candidates for advanced energy storage applications, including next-generation batteries and supercapacitors.
The intersection between molecular magnetism and porous nanotechnology opens a fascinating field with immense technological potential. From sensors that can distinguish molecules by their magnetic behavior to computer memories that consume a hundred thousand times less energy, these materials promise to transform fundamental technologies in the coming decades.
As one research team observed, the true power of these materials lies in their ability to reversibly change their properties in response to external stimuli, such as the presence of specific gases 2 . This adaptability, combined with the persistence of magnetism at room temperature, makes magnetic nanoporous materials one of the most exciting frontiers in current materials science.
As the proverb says, "holes are not shortcomings, but opportunities"... and in this case, nanometric holes could be the key to new technologies that today we can only imagine.