Highly compressible ultra-light anisotropic cellulose/graphene aerogel fabricated by bidirectional freeze drying for selective oil absorption

Low density aerogels are promising materials for oil absorption, but they typically suffer from low compressibility and elasticity. Herein, three-dimensional (3D) highly compressible, elastic, anisotropic, cellulose/graphene aerogels (CGAs) were prepared by bidirectional freeze drying. After the grafting of long carbon chains through chemical vapor deposition, the modified cellulose/graphene aerogels (MCGA) gained superhydrophobicity. The synergistic effects of flexible cellulose, stiff graphene, and the special bidirectionally aligned porous structure gave MCGA outstanding compression and recoverability properties. MCGA was able to recover 99.8% and 96.3% when compressed to 60% and 90% strain, respectively. Due to its ultra lightweight (bulk density of 5.9 mg/cm³) and high surface area (47.3 m²/g), MCGA possesses a remarkable absorption capacity of 80–197 times its weight, which surpasses all hydrophobic cellulose aerogels and most carbon-based aerogels. Furthermore, the high elasticity of MCGA facilitates fast and efficient recovery of the absorbed oil by simple mechanical squeezing, and ensures excellent performance stability over repeated use. The high compressibility and high oil recovery ability though mechanical squeezing has never been achieved by other aerogels. Hence, MCGA can serve as a promising super absorbent material for selective oil absorption and recovery.