The use of lignocellulosic materials for extracting functionalized cellulose nanocrystals (FCNs) in a green and sustainable method under mild conditions is limited owing to the strong hydrogen bonding in cellulose. Up to now, the economic and sustainable production of CNCs in a green approach together with a high yield is not facile and remains a challenge. A facile, green, and high-efficient avenue was developed to produce FCNs with high yield through the mechanochemistry synergetic effect of recyclable p-toluenesulfonic acid (PTSA)-catalyzed deep eutectic solvent (PDES) and microwave- solvothermal (MWS). The combination of PDES and MWS treatment created a mechanochemical synergetic effect on disintegrating the supramolecular structure of cellulose and contributing to the improvement of reaction efficiency, resulting in the simultaneous hydrolysis and oxidation of cellulose in the one-step mechanochemical processing. A high yield of 87.6% of FCNs was obtained, and the rod-like FCNs had a diameter of 9 nm and length of 120-150 nm, and showed high charge density (1.59 e nm-2), high crystallinity (81%), high thermostability (>335 ℃), and good dispersibility in water. When a loading of 1 wt % FCNs was added into gelatin matrix, the tensile strength and Young’s modulus of the bionanocomposites increased 188% and 131% respectively, suggesting their remarkable stress transfer potential. The outstanding reinforcing effect of FCNs in the gelatin matrix confirmed their remarkable enhanced capability and displayed strong potential in constructing advanced bionanocomposites. Furthermore, The PDES could be directly reused four times and was easy to be recovered, and thus was beneficial to cost reduction and waste liquor treatment. Subsequently, facile and efficient recovery of PTSA and formic acid were accomplished through recrystallization and evaporation respectively. It was found that the recovery yield of PTSA could be reached 90%. The recycled PTSA was used to manufacture FCNs for the next cycle, and thus reducing the pollutant emissions, saving cost, and realizing green production of functionalized cellulose nanocrystals. Therefore, the study may provide a green, sustainable, and cost-effective way for the large-scale production of FCNs, contributing to strong potential in building high-performance bionanocomposites and broaden the diversified applications of FCNs in nanocomposites.

Cellulose nanocrystals,High yield,P-toluenesulfonic acid catalysis,Deep eutectic solvent,Mechanochemistry