Catalysts are central to many industrial chemical processes. Among these, the synthesis of ammonia; used largely for fertilizers; consumes a large share of global energy. This team led by Leticia González (Faculty of Chemistry) and Georg Kresse (Faculty of Physics) at the University of Vienna has recently used quantum mechanical modeling to clarify how a particular iron-based catalyst, called MIL-101(Fe), works at the atomic level. Their findings could help improve catalyst design and reduce energy loss in chemical manufacturing.
Lechner, P., Ganguly, G., Sahre, M. J., Kresse, G., Dietschreit, J. C. B., & González, L. (2025). Spin Frustration Determines the Stability and Reactivity of Metal–Organic Frameworks with Triangular Iron(III)–Oxo Clusters. Angewandte Chemie International Edition. https://doi.org/10.1002/anie.202514014
The material MIL-101(Fe) is a metal-organic framework (MOF) built from iron atoms arranged in sets of three around a central oxygen atom forming “triangular” clusters. Earlier work, both experimental and theoretical, assumed that these three iron atoms carry spins (tiny magnetic moments) aligned in parallel (a “high-spin ferromagnetic” configuration). What the Vienna group found overturns that assumption. Their computations show that the true ground state is one in which the iron atoms are aligned mostly antiparallel to one another; but because of their triangular arrangement, perfect antiparallel alignment is impossible for all three at once. Two of the iron atoms can oppose each other, but the third must compromise. This condition is called spin-frustration.
Leticia González (Faculty of Chemistry) from the University of Vienna stated,
“This magnetic frustration, which can only be explained through a superposition of different quantum states, stabilizes the structure of the catalyst and enables a particularly efficient interaction with small gas molecules such as N2 and CO; which accounts for its catalytic activity.”
Moreover, the research indicates that treating MIL-101(Fe) with the standard assumptions (ferromagnetic, high spin) leads to errors in predicted structure, stability, and how well it binds small gas molecules such as nitrogen (N₂) and carbon monoxide (CO). By using a refined density functional theory (DFT) approach; one that allows “flip-spins” or broken symmetry configurations; they identified a spin-frustrated antiferromagnetic state with multiplicity M = 6 as the more accurate ground state.
This spin-frustration has practical implications. It appears to improve how MIL-101(Fe) binds N₂ under ambient conditions, a critical step for catalytic ammonia formation. When the material is partially reduced (so one iron center changes oxidation state), that spin-frustration diminishes, and the catalyst’s behavior shifts: N₂ binding weakens while CO binding becomes more favorable. These shifts help explain experimental trends that were previously not well accounted for in simple models.
For engineers and materials scientists, this work highlights two important lessons. First, computational models that ignore spin-frustration can mispredict which catalyst structures are stable and how they will behave under working conditions. Second, the performance of catalysts depends not only on their chemical composition but also on how their magnetic and electronic states are configured. An accurate design of MOFs like MIL-101(Fe) may require explicitly accounting for possible spin arrangements and their temperature or oxidation-state dependence.
Looking ahead, further work will need to test how these quantum mechanical insights translate under real operating conditions: varying temperatures, pressures, gas mixtures, and in catalytic cycles. Experiments that probe spin states directly (for example via magnetic measurements or spectroscopic methods) will help confirm the theoretical predictions.
This study, moves our understanding of iron-based catalysts forward by revealing that spin-frustration and quantum superposition are not just theoretical curiosities but foundational to how certain catalysts work. As industry seeks cleaner and more efficient catalytic processes, such insights will be increasingly relevant.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
