An inexpensive novel membrane driven by a difference in humidity, grabs carbon dioxide out of air. It’s the first synthetic membrane able to do this and also increase the gas’ concentration without requiring energy for operation. Using a special molten-carbonate membrane, scientists employed a laser to drill hundreds of small, conical pores in an alumina tube and fill the material with a molten carbonate salt. Then, they applied a humidity difference across this membrane so that it has a dry air input stream and wet air output stream. The membrane uses this humidity difference to spontaneously pump CO2 uphill from the dry input stream to the membrane’s higher humidity side. More work needs to be done, but it’s promising.
www.ncl.ac.uk/press/articles/latest/2024/07/humidity-drivenmembrane/