Synthesis of Mimicking Plant Cell Wall‐Like Anti‐Swelling Hydrogels Based on a “Bottom‐Up” Strategy and Their Application in Osmotic Energy Harvesting

Abstract Osmotic energy harvesting via reverse electrodialysis (RED) presents a promising approach for converting salinity gradient energy into usable power. However, the broad implementation of this technology faces significant barriers, including the inherent instability of conventional ion‐selective membranes, the intricacy of fabrication techniques, and unresolved environmental challenges. This hydrogel combines the structural and adhesive properties of carboxymethyl cellulose (CMC) and double‐bond lignosulfonate sodium (DLS) to enhance antiswelling performance. DLS is functionalized through a hydroxyl‐alkyne click reaction, transforming it into a highly reactive supramolecule. Simultaneously, CMC is integrated into the gel network using a choline chloride/acrylic acid deep eutectic solvent, where acrylic acid acts as both a hydrogen bond donor and a polymerizable monomer. The resulting hydrogel demonstrates remarkable ion selectivity and efficient osmotic energy harvesting, achieving an ultralow swelling rate of 0.385, an output power density of 10.10 W m ^{− 2} (double the commercial benchmark of 5.0 W m ^{− 2} ), and an ion selectivity of 99.10%. This study underscores the potential of biomass‐based hydrogels as sustainable, high‐performance materials for osmotic energy harvesting, offering a viable pathway for next‐generation energy technologies.