Controlled Sol–Gel Transitions of Metal–Organic Membrane-Enveloped Cellulose Nanofibrils via Metal Coordination in Aqueous Media

We report a metal coordination-driven sol–gel transition system where cellulose nanofibrils are enveloped by a rationally designed metal–organic membrane (MOM) in an aqueous medium. Specifically, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) is encapsulated within an MOM comprising Zn2+and the chelator phytic acid (PA), denoted TOBCMOM. Using the DLVO theory, we elucidate how tuning the metal ion valence in TOBCMOMmodulates the sol–gel transition by controlling interfibrillar attractive forces. Notably, TOBCMOMfluids exhibit relaxation times consistent with the Kohlrausch–Williams–Watts (KWW) function. Significantly, we demonstrate reversible, sustainable sol–gel transitions in TOBCMOMunder stepwise mechanical strain. This facile approach enables rheological tailoring of aqueous media, promising for the development of advanced stimuli-responsive smart fluids for applications in cosmetics, food science, and pharmaceutical formulations.