Boron-rich COF as a structured porous cross-linker decouples mechanical robustness and ionic conduction in eutectogels

Although boron-based cross-linkers (e.g., boric acid, borax) are widely used to enhance gel mechanics through dynamic B O bonds, their small-molecule nature inevitably causes leaching and disrupts ion transport, leading to a persistent trade-off between robustness and conductivity. Herein, we overcome this limitation by designing a boron-rich covalent organic framework (COF-1) as a structured porous solid cross-linker for cellulose-based eutectogels. The eutectogel is fabricated through facile dissolution of cellulose in a ternary ZnCl 2 /formic acid/water deep eutectic solvent, followed by incorporation of boron-rich COF-1. The rigid COF-1 scaffold, abundant in surface boroxine rings, forms dense and homogeneous B–O···H–O hydrogen bonds with the cellulose matrix, serving as robust junctions that enhance mechanical strength. The tensile and compressive strength of COF-1 reinforced eutectogel can reach 0.34 and 1.95 MPa, respectively. Crucially, its inherent 1.5-nm nanochannels of COF-1 provide dedicated pathways for rapid Zn 2+ migration, enabling high ionic conductivity (4.23 S·m −1 ). This dual functionality effectively decouples mechanical and conductive properties. The resulting gel exhibits high sensitivity, temperature tolerance, and stability as a flexible sensor, establishing a paradigm of porous solid cross-linkers for next-generation soft materials.