Metal-organic skeleton and woven nanocellulose layers are perfectly blended to improve the self-lubrication behavior of flexible polymers

The waste products of agroforestry production and processing (stalk, straw, hulls, wood flour) are often considered to be worthless materials and are usually buried or burned. A few valuable by-products can be further utilized and used for chemical composting or handicrafts. Herein, the deep eutectic solvent (DES) defibrillation and chlorine-acid oxidation processes were used to crack and remove lignin of waste poplar powder to obtain esterified nanocellulose (NC). A further ice-template method was used to construct 2D woven NC layers with transversely large-sized structures. The ZIF-8 nanoparticles and polydopamine (PDA) coatings were sequentially grown on the NC layer surface to obtain NC@ZIF-8/PDA hybrid composites. The ZIF-8 nanoparticles have high negative amount on NC layer surface, and the PDA coatings enhanced the mechanical stability of the hybrid NC@ZIF-8/PDA and prevented the degradation of ZIF-8 in water condition. Importantly, NC@ZIF-8/PDA was introduced into PVA matrix to obtain NZPP films which shows the high tensile strength (101.58 MPa), excellent elongation at break (202.8 %) and toughness (152.52 MJ/m 3 ), high impact strength (68.9 KJ/m 2 ), and self-lubricating capability. The highly woven and entangled NC layers and ZIF-8 with internal pore structure produces fine structural changes and spatial constraints under applied loads and shear stresses, which leads to irregular deformation of the friction contact surface, thus accelerating the distribution of friction stresses and friction energy transfer.