The selective extraction of particular gas molecules from gaseous mixtures is a challenging chemical problem with significant environmental and economic benefits for success. For instance, capturing carbon dioxide (CO2) from the atmosphere or industrial exhaust gases could aid in reducing climate change.
Together with colleagues from China, researchers from Kyoto University present a novel and energy-efficient solution in the journal Nature Communications.
Our work demonstrates exceptional molecule recognition and separation performance by deliberately organizing the pore geometry, structural flexibility, and molecular-level binding sites within a porous coordination polymer (PCP).
Susumu Kitagawa, Chemist, Institute for Integrated Cell-Material Sciences, Kyoto University
Susumu Kitagawa led the research group.
Metal ions or clusters are held together by organic (carbon-based) linker groups in PCPs, also known as metal-organic frameworks (MOFs). It is possible to produce a huge variety of crystalline materials with pores that have precisely controlled sizes, structures, and chemical binding abilities by selecting various metallic components and modifying the size and structure of the organic groups. With pores that change when specific molecules bind to them, the new research goes beyond that.
We designed a flexible PCP with a corrugated channel system that can interact with and adsorb CO2 molecules by selectively opening pores that acts as gates, allowing only the CO2 to pass through.
Ken-ichi Otake, Kyoto University
He explains that CO2 capture is particularly difficult due to the molecule’s small size and low affinity for many adsorptive materials.
Exclusion discrimination gating is the technical term for what the interaction between CO2 and PCP achieves. This implies that binding of the extraction target molecules, here CO2, causes a synergistic structural change that improves binding and opens up the solid phase structure to allow the bound molecule to enter.
The team used their system to extract CO2 from mixtures containing many industrially significant molecules, such as methane, nitrogen, oxygen, carbon monoxide, hydrogen, ethane, argon, ethene, and ethyne. This served as a demonstration of the system’s effectiveness.
Over the course of a complete cycle of selective gas capture and regeneration, the procedure is significantly more energy efficient than the alternatives. This may be crucial for creating more environmentally friendly gas separation technologies that can aid in developing low-carbon industrial processes. Any significant climate engineering efforts to remove carbon dioxide from the atmosphere will also depend on energy efficiency. These will not be viable options if producing a lot of energy is necessary to run the cycle of extraction, release, and storage.
By building on this initial success, future research will hopefully achieve more versatile breakthroughs in a wide range of selective gas extraction processes.
Yifan Gu, Study First Author and Postdoctoral Researcher, Kyoto University
Gu, Y., et al. (2023). Soft corrugated channel with synergistic exclusive discrimination gating for CO2 recognition in gas mixture. Nature Communications. doi.org/10.1038/s41467-023-39470-w.