Neutral and natural xylose-based deep eutectic solvents facilitating efficient modification-free production of...

Holocellulose nanofibrils (HCNFs), a group of novel bio-based nanomaterials containing hemicellulosic polysaccharides, have exhibited inherent sustainability, biodegradability, and superior mechanical properties compared to cellulose nanofibrils, demonstrating significant potential for applications in advanced materials. However, conventional HCNFs production often causes serious degradation of hemicelluloses, inevitably surface modification of raw cellulose and solvent pollution, etc. Herein, neutral and natural deep eutectic solvents (NADESs) combined with choline chloride (ChCl) and xylose (Xyl) are firstly proposed for preparation of bamboo HCNFs, which result in high hemicellulose content of ~19%, cellulose degree of polymerization (DP) preservation of 95%, and the well preservation of surface hydroxyl groups of pristine holocellulose in bamboo cell wall. The NADESs treatment-induced HCNFs displayed the highest aspect ratio of ~115, indicating robust protection of its molecular integrity. Tough films of HCNFs with good transparency (60%-80%), high tensile stress (122.34 MPa) and toughness (44.13 MJ/m³) were facilely prepared. Molecular simulation analysis was carried out for the mechanisms on bamboo holocellulose nanofibrillation, proving notable weakening of the intermolecular hydrogen bonds interactions by the NADES. Cellulose chains exhibit a stronger preference for forming hydrogen-bonding interactions with Xyl than with ChCl. The hydrogen bond density between cellulose chains and xylose is significantly higher, 2.8 times that of which between cellulose chains and ChCl. suggesting the excellent capability of ChCl: Xyl DES to dissociate cellulose microfibrils while retaining hemicellulose components. Thus, this study deepens the understanding of novel DES treatment on lignocellulosic biomass and broadens the scope of universal utilization of plant polysaccharides.