The study presents a cutting-edge, sustainable approach for the high-yield production (59-62 %) of carboxyl-functionalized cellulose nanocrystals (CNCs) with impressive aspect ratio (20.65 ± 0.74 nm), high crystallinity (77-81 %), outstanding thermal stability (290 °C-343 °C) and varying degrees of functionalization. This innovative method harnesses the synergistic power of mild organic acid hydrolysis (10 %) and steam explosion, employing eco-friendly acids such as acetic, citric, malic, tartaric, and oxalic. These acids drive efficient esterification, as evidenced by zeta potential values (-16 mV to -34 mV) and the presence of ester carbonyl peaks in IR spectroscopy (1730 cm