Researchers from Tomsk Polytechnic University jointly with their colleagues from the Czech Republic have found a method to synthesize cyclic carbonates from atmospheric CO2. Cyclic carbonates are organic compounds, used as electrolytes for lithium-ion batteries, green solvents as well as in pharmaceutical drugs manufacturing.
The scientists managed to synthesize carbonates under sunlight and at room temperature, while conventional methods require synthesis under high pressure and temperatures. The research findings are published in the Journal of Materials Chemistry A (IF:11,301; Q1).
“The increase in CO2 levels in the atmosphere is a global environmental problem. The solutions of the problem are usually focused on measures to reduce CO2 emissions. An alternative method is to use the CO2 already existing in the atmosphere for useful chemical transformations. Thus, we offered a new method allowing to obtain widely sought-after cyclic carbonates under sunlight. Most often, such reactions are carried out at high temperatures ranging from 60°С to 150°С and high CO2 pressure up to 25 atm. It means the technological chain requires additional equipment for CO2 compression and heating. In other words, it is impossible to simply extract it from the air,” Olga Guselnikova, Research Fellow of the TPU Research School of Chemistry and Applied Biomedical Sciences, one of the authors, says.
As a result of the experiments, the scientists synthesized cyclic carbonates from the interaction of CO2 and epoxides, used as starting materials.
“To begin with, we had to capture CO2. In order to do that, we used gold nanoparticles grafted with organic nucleobases. They served as traps for CO2 molecules and, at the same time, remained non-reactive with other substances. The experiments showed that these traps efficiently captured CO2 from the air. We mixed the suspension from the nanoparticles and captured CO2 with epoxides,” Pavel Postnikov, Associate Professor of the TPU Research School of Chemistry and Applied Biomedical Sciences, says.
Then, the researchers irradiated this mixture with infrared light.
“The gold nanoparticles possess a plasmonic effect. It means the incident light excites plasmonic quasiparticles next to gold nanoparticles and the plasmonic quasiparticles trigger the reaction. They convert light energy into the energy required for the chemical reaction. These properties allowed conducting the reaction under ambient conditions. By the way, the matter of plasmonic chemistry mechanisms, how plasmons actually trigger chemical processes and how it works is a trending scientific topic. A number of our previous articles relate to this field of research. Control experiments allowed us to suggest that plasmon excitation on particles leads to the transfer of energy to the captured CO2 molecule without heating,” Olga Guselnikova says.
As the authors of the article note, the synthesis process is comparable with similar methods, however, it does not require special technologically sophisticated equipment.
“The entire process takes about 24 hours, while regular indicators for other methods vary from 12 to 24 hours. We started from small volumes and received a few millilitres of cyclic carbonates. However, we explicated in the article that the method can be scaled up at least fivefold and nanoparticles themselves can be reused with the same efficiency. At the same time, the catalytic indicators of our plasmonic system are among the highest recorded ones for the reaction. The most important is to demonstrate an opportunity to conduct the reaction directly with the air without prior purification or CO2 concentration under ambient conditions and sunlight. Ultimately, it always makes the synthesis more simple and eco-friendly,” Pavel Postnikov adds.
The research was conducted jointly with the scientists from the University of Chemistry and Technology, Prague and Jan Evangelista Purkyne University (the Czech Republic) with the support of the Russian Science Foundation.