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A robust mixed metal-organic framework for CO2 absorption and conversion

The challenge

Metal organic frameworks (MOFs) are a promising material for the capture and storage of CO2 due their highly porous nature. Importantly, by incorporating metal nanoparticles within the MOF structure,  the stored CO2 can be catalytically converted in-situ to industrially useful feedstock gases such as methane and carbon monoxide. This tantalizing combination of capture and conversion of CO2  represents a sustainable, economically attractive solution to addressing CO2 emissions. Despite this, incorporating metal nanoparticles into MOFs is challenging, with many synthesis routes either expensive/complex or resulting in large nanoparticles that exhibit minimal catalytic activity.

The solution

Researchers from the school of Chemical Engineering at UNSW and CSIRO recently have shown that a mixed metal precursor MOF containing both nickel and magnesium, NiMg-MOF-74, can simply be heated at low temperature (350 °C) to create a novel hybrid material which efficiently captures and converts CO2 to methane and carbon monoxide.

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To understand the underlying mechanisms, both the precursor and its sintered version were investigated using a variety of synchrotron based spectroscopic techniques, including Near Edge X-ray Absorption Fine Structure (NEXAFS) at the Soft X-ray Beamline. The NEXAFS data showed conclusively that not only was the magnesium within NiMg-MOF-74 unaffected by the heating process, but that much of the nickel was converted from Ni2+ into a metallic form. Electron microscopy rounded out the investigation, confirming that the metallic nickel was in the form of nanoparticles, distributed throughout a Mg-based MOF architecture. These results help to explain the efficient catalytic activity, with the researchers able to identify the optimal ratio of nickel to magnesium in NiMg-MOF-74 for obtaining the highest storage and conversion activity.

MOF

The impact

This work has shown that mixed-metal MOF template materials such as NiMg-MOF-74 can be used to create a metallic nanoparticle network contained within the MOF architecture for CO2 capture and conversion. Indeed, as recognized by the 2025 Nobel Prize in Chemistry, MOFs are inherently versatile in their construction, which greatly aids in tailoring these functionalized structures. Overall, this work helps to bridge an important functional gap between carbon capture and conversion, with a range of applications including air purification, heterogeneous catalysis, sensing and energy storage.

This case study, written by Dr Anton Tadich was the winner of ANSTO Australian Synchrotron's Case Study Competition Round 3 2025. 

References:
T. Zurrer, K. Wong, J. Horlyck, E. Lovell, J. Wright, N. Bedford, Z. Han, K. Liang, J. Scott and R. Amal (2021) Mixed-Metal MOF-74 Templated Catalysts for Efficient Carbon Dioxide Capture and Methanation Advanced Functional Materials, 31, 2007624 https://doi.org/10.1002/adfm.202007624  

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