A team of chemists from the UK Catalysis Hub and the University of Salford have studied materials at the molecular level to find out how defects in copper can assist with CO₂ capture.
In addition to reducing our greenhouse gas emissions, we can also mitigate the harmful effects of excess CO₂ - and create added value - by capturing it from the atmosphere for storage and reuse.
In a new study published in Materials Advances, researchers used computational analysis as well as real-life experiments to determine which structural features of a Cu-MOF (a copper based metal-organic framework) were involved in the capture of CO₂. They found that imperfections in the copper atoms played an important role, with more defects allowing for higher adsorption of CO₂.
These findings are the result of many years of collaboration across the UK and beyond, encompassing work from final-year undergraduate projects and PhD theses. Salford group leader Dr Rosa Arrigo explains how facilities at RAL enabled the in situ analysis for this study:
World-class facilities like Diamond Light Source and ISIS Neutron and Muon Source are revolutionising how we study materials chemistry.
Diamond’s synchrotron X-rays enable us to probe the electronic structure of materials with the highest resolution of chemical states in space and time, and are uniquely suited to investigating dynamic processes within solids. Together, these tools allow us to capture fast and complex phenomena, such as bond breaking and making, and thus study how materials behave and evolve under realistic environmental conditions.
Our collaborative study demonstrates how these national facilities at RAL were essential for probing the local environment of copper sites in our MOF material and for understanding the dynamic changes occurring during CO₂ adsorption. Through this analysis, we were able to inform the computational modelling and derive the nature of the active sites that reproduced the behaviour of the material with the highest atomic structural detail. This work exemplifies how access to advanced instrumentation empowers transformative research in materials chemistry.
The UK Catalysis Hub is embedded amongst this advanced instrumentation thanks to their base at Research Complex at Harwell, where lead author Dr Lotfi Boudjema arrived as a visiting researcher from UCL in 2021, he explains:
The Catalysis Hub and the facilities at RAL were vital to our experiments, providing the advanced capabilities needed to investigate the material’s structure and properties in depth. Their support was key to the success of this collaboration.
What next for these results? The study shows a trade-off between performance and stability of the materials, linked to the nature and abundance of defects. The researchers found that a rapid microwave-assisted solvothermal synthesis is a suitable method to generate these defects. This is important for industry, allowing for an efficient and cost-effective way of producing the material.
One hurdle still to overcome is that the MOF was found to work better in dry conditions, as water competes with CO₂ for the adsorption sites.
This research presents an important synthetic and methodological approach for investigating MOF materials. Future research can follow in these footsteps to address CO2 capture capacity and water stability - an essential step towards real-world application.
