A hydrazone-carboxyl ligand-linked cellulose nanocrystal aerogel with high elasticity and fast oil/water separation

In this work, we present a new feasible way to synthesise cellulose nanocrystal (CNC) aerogel by the use of the secondary building units (organic carboxyl ligand), what had been extensively used in the building of cubic-structured metal organic frameworks (MOFs). The linear paddle-wheel structure of NHNH₂–BDC–NHNH₂ endows CNC aerogels with high elasticity and fast oil/water separation. The porosity and density of CNC aerogels could be regulated by different contents of NHNH₂–BDC–NHNH₂ and CHO–CNCs. Three mixing methods, such as vortexing, double-barrel blending and sonication, were carefully performed to investigate their formation of CNC aerogels. The density of the aerogels ranged from 22.4 to 23.3 mg/cm³ and specific surface areas were 195–303 ± 10 m²/g characterized by Brunauer–Emmett–Teller analysis. The structural analysis of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the bimodal pore distribution and the hydrazone-carboxyl ligand-linked structure. On the basis of the porosity of 96.3–97.2%, the absorption capacity of aerogels was 133 ± 6 g/g for water, was 99 ± 8 g/g for ethanol, was 34 ± 4 g/g for toluene, and was 54 ± 6 g/g for dodecane. The CNC aerogels showed excellent mechanical properties and shape recovery ability in water and air. Meanwhile, the results indicate that more carboxyl on organic linkers can improve the properties of elasticity and separation for aerogels.