Unique CO₂ adsorption behavior of wild silk cocoons

Wild silk cocoons are light-weight composite structures with unique properties. One such property is the intriguing CO₂ gating property (i.e., unidirectional flow of CO₂) exhibited by the wild Antheraea pernyi (A. pernyi) silkworm cocoon. This study investigated the hierarchical structural and compositional features of A. pernyi cocoons and their impact on CO₂ adsorption. For the first time, soap-film flowmeter testing method and gas permeability testing method were used to quantitatively demonstrate the A. pernyi cocoons’ CO₂ adsorption property and selectivity for gas mixture. The results showed that the multi-layered composite structure of A. pernyi cocoons, coupled with calcium oxalate crystals, play a crucial role in their CO₂ adsorption and separation performance. These findings shed light on the unique functional design of wild silk cocoons and provide a new biomimetic approach for developing materials and structures to address global challenges such as CO₂ capture and storage.