Expandable and scalable production of cellulose nanofibrils via highly efficient swelling-modification in deep eutectic solvent

The scalable production of chemically tailored cellulose nanofibrils (CNFs) remains challenging because native cellulose lacks sufficient chemical versatility for simultaneous fibrillation and functional regulation. Here, we develop a highly efficient swelling-modification strategy using a hydrated deep eutectic solvent (Zn(OAc)2/ChCl/H2O) to enable efficient CNF production and programmable chemical modification. Zn(OAc)2 regulates proton activity through buffering effects, suppressing excessive hydrolysis and preserving the crystalline structure of CNFs with an ultrathin diameter (3–4 nm), high aspect ratio (~1800), high degree of polymerization (600–900), and high yield (93%). By incorporating diverse cyclic anhydrides, this DES system is transformed into a multifunctional operating platform, enabling customizable CNFs with diverse chemical functionalities, including carboxyl groups, double bonds, bridged bicyclic structures, and aromatic rings. This highly efficient swelling-modification strategy provides a scalable and expandable route toward customized CNFs, advancing the design of cellulose-based functional nanomaterials. Deep eutectic solvents enable sustainable, scalable production of cellulose nanofibers, but current systems are acidic, degrading the cellulose. Here, the authors use a pH buffering deep eutectic solvent to obtain cellulose nanofibrils with high aspect ratios and degrees of polymerisation.