Carbon dioxide (CO2) is the primary greenhouse gas produced by human activity and researchers have long sought ways to mitigate its environmental impact. Scientists have also explored ways to not only reduce and contain CO2 emissions, but also repurpose them as new resources for energy and functional materials. Researchers at Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) have now presented a one-pot method for synthesizing porous metal-organic frameworks (MOFs) from CO2 at ambient temperature and pressure.
Due to CO2’s natural inertness and stability, repurposing it for MOF synthesis under ambient conditions was a challenging task. To facilitate the reaction, the researchers passed CO2 through a solution with the organic molecule piperazine at a temperature of 25°C and pressure of 0.1 MPa. The chemical composition of the solution was tuned to enable the reaction between piperazine and CO2, forming carbamate bonds linking together the crystalline structure. This process caused the white microcrystalline powder to form quickly, which was collected and dried before analysis.
Multiple analytical methods were used to characterize the structure and properties of the powder, including powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy and X-ray absorption spectroscopy. The analyses confirmed the formation of highly porous, cubic Zn4O(piperazine dicarbamate)3 frameworks with bridging dicarbamate linkers, high surface area and high CO2 content. The method and results were published in the Journal of the American Chemical Society.
High purity CO2 was used in this experiment, but the researchers are now exploring how to replicate the process using CO2 from the air and from fossil fuel emissions.
“Direct utilization of CO2 is challenging, but it will potentially save a lot of energy that is required for the capture and separation of the gas,” said Satoshi Horike, who led the study. “The emission of CO2 by fossil fuel combustion must be reduced and regulated to protect the environment. Our method here is a potential clue to help solve some important environmental problems.”
The researchers chose to synthesize MOFs due to their functionality in a number of applications, including as biosensors, catalysts and storers of gas. Reusing CO2 from emissions to produce functional materials would not only help the environment but provide a renewable resource for the production of new technologies.