The orange balloon on the left illustrates this point as a higher volume of nitrogen gas is able to pass through PIM-1 into the balloon compared with the membrane on the right, connected to the pink balloon.

The most abundant greenhouse gas is carbon dioxide, which made up 84% of the United States' greenhouse gases in 2012, and can linger in Earth's atmosphere for up to thousands of years.

The PIM-1 membrane is "typically embedded with a network of channels and cavities less than 2 nm in diameter that can trap gases of interest once they enter," said Qilei Song, who was involved in the study at the university's Institute for Integrated Cell-Material Sciences (iCeMS) and the University of Cambridge in the UK. "The only problem is that their intrinsic properties make them rather flimsy and their starting selectivity is weak."

To overcome PIM-1's weaknesses, Sivaniah's team heated PIM-1 at temperatures ranging from 120 to 450°C in the presence of oxygen, a process referred to as thermal oxidation. "Oxygen, under high temperatures, chemically reacts with PIM-1 to reinforce the strength of channels while controlling the size of so-called gate openings leading into the cavities, which allows for higher selectivity," said Song.

Fossil fuels

The resultant membrane was found to be twice as selective for carbon dioxide while allowing air to pass through it 100 times faster compared with commercially available polymers. PIM-1 can also be used for other applications such as capturing carbon dioxide from the burning of fossil fuels, enriching the oxygen content in air for efficient combustion engines, hydrogen gas production, and processes to generate plastic.

"Basically, we developed a method for making a polymer that can truly contribute to a sustainable environment," said Easan Sivaniah, associate professor at Kyoto University, who headed the research team. "And because it is affordable and long lasting, our polymer could potentially cut the cost of capturing carbon dioxide by as much as 1000 times."

The findings were published in the UK journal Nature Communications.