As shown in Fig. 3a, the CA, has a weight of 9.84 × 10−2g, is lightweight and has a low density of ∼18.5 mg cm−3 calculated based on Archimedes’ principle. The WNP fiber aerogel, consists of a large amount of cellulose, can absorb water effectively due to the hydrophilic character of cellulose. On the contrary, the CA is hydrophobic. The water repellency of the CA highlighted in Fig. 3b,water droplet exhibit typical spherical shape on the CA surface, and the reflective, bright surface visible underneath the water droplet is a symbol of trapped air and the formation of composite solid–liquid–air interfaces. The inset in Fig. 3b shows an image of the water contact angle of the CA, and the water contact angle is 132◦. To further confirm the hydrophobicity of the CA, it was held by a pair of tweezers, submerged in water, and its surface acts like a silver mirror when viewed at a glancing angle(Fig. 3c), due to the establishment of an interface between the entrapped air in the 3D CA and the surrounding water. Once the external force was released, the CA could float immediately on the surface of water without the absorption of water as represented in Fig. 3d, indicating that the CA is lightweight mentioned earlier.