Atmospheric carbon dioxide is a major contributor to climate change. Methods for preventing emissions and capturing CO₂ are, thus, important. Zeolites, for example, could be useful as efficient adsorbents for CO₂. However, zeolites are difficult to process, which makes it challenging to turn them into, e.g., gas filters.

Luis Valencia, Stockholm University, Sweden, Anders E. C. Palmqvist, Chalmers University of Technology, Gothenburg, Sweden, and colleagues have developed hybrid foams for selective CO₂ sorption in which microporous zeolites are supported on a mesoporous/macroporous material. The team used the zeolite silicalite-1 and loaded it onto the support material, which was prepared from TEMPO-oxidized cellulose nanofibers (TOCNFs) and gelatin. The resulting foams were freeze-dried.

The researchers achieved ultrahigh zeolite loadings up to 90 wt% in the foams. The hierarchical porosity of the material allows for fast gas diffusion, while the support provides mechanical stability. The CO₂ capacity of the foams goes up linearly with the zeolite content, which shows that the support does not interfere with the adsorption. The material shows a high selectivity for CO₂ over N₂ adsorption.

• Bio-based Micro-/Meso-/Macroporous Hybrid Foams with Ultrahigh Zeolite Loadings for Selective Capture of Carbon Dioxide,
  Luis Valencia, Walter Rosas, Andrea Aguilar-Sanchez, Aji P. Mathew, Anders E. C. Palmqvist,
  ACS Appl. Mater. Interfaces 2019.
  https://doi.org/10.1021/acsami.9b11399