This study fabricated choline–acrylic acid deep eutectic solvent (DES) hydrogels via in situ free-radical polymerization and systematically investigated the individual and co-optimization effects of lignin dosage and water content on the chemical structure, micromorphology, compressive mechanical properties, swelling behavior, and thermal stability of the hydrogels. This work quantitatively uncovers the co-optimization mechanism between the two variables in modulating crosslink density and pore architecture, thereby filling a research gap in the dual-factor co-optimization of biomass-based DES hydrogels. The results reveal that a moderate lignin dosage (0.02 g) generates abundant dynamic hydrogen bonds, densifying the crosslinked network and raising the maximum compressive stress from 0.378 MPa to 0.426 MPa, whereas excessive lignin triggers molecular aggregation and deteriorates mechanical performance. Higher water content dilutes crosslinking sites, reduces network compactness, boosts the swelling ratio while lowering compressive strength, and exerts negligible impacts on thermal degradation characteristics. FTIR analysis confirms that lignin participates in network formation solely through non-covalent hydrogen bonds, without forming new covalent bonds. A comprehensive performance evaluation identifies the optimal formulation as 0.02 g lignin and 60 g water. Although this two-factor optimization strategy provides clear experimental and theoretical guidance for designing sustainable soft materials, the present work still has limitations, including the use of only static laboratory characterizations, with no cyclic mechanical measurements or aging assessments. This study advances the customized performance tuning of lignin-derived DES hydrogels and facilitates the high-value valorization of lignin, which is promising for multifunctional green-material applications, including adsorption, flexible electronics, and biological carriers.

To address the limitations of conventional polymer hydrogels in terms of sustainability and functionality, green soy protein (SP)-based hydrogels (SPHs) demonstrate significant potential. As an abundant, renewable plant protein, SP provides an ideal molecular platform for constructing high-performance, multifunctional hydrogels. This review systematically consolidates recent progress in SPHs. Firstly, the molecular fundamentals and gelation mechanisms of soy protein are analyzed in depth. Subsequently, key construction strategies, including physical, chemical, and enzymatic crosslinking, as well as composite/hybrid approaches, are comprehensively reviewed with respect to their mechanisms, advantages, and limitations. Following this, innovative applications of SPHs in biomedical, food and nutrition, environmental/agricultural, and smart material fields are highlighted. Finally, the current challenges facing research in mechanical properties, structure–property relationships, and scalable production are identified. Future directions include developing novel green crosslinking systems, deepening multi-scale structural control, and advancing smart integrated design. This review aims to provide researchers with a systematic knowledge framework spanning from “molecular understanding” to “functional customization,” thereby propelling soy protein hydrogels toward higher toughness, intelligence, and sustainability.

Wood aerogel has emerged as a highly promising substrate for advanced adsorbents due to its green nature, low cost, high porosity, and unique three-dimensional (3D) interconnected network structure. Harnessing forest resources for developing high-performance aerogel materials is crucial for tackling organic dye pollution. This study presents a novel aminated wood-based aerogel engineered through the co-deposition of tannic acid (TA) and polyethylenimine (PEI) on a cellulose skeleton. The fabrication involved a top–down delignification process to create a porous wood aerogel framework, followed by the in situ loading of TA and the grafting of amino-rich PEI, resulting in the final TAPI-DW composite. Benefiting from the abundant active sites deposited on the aerogel’s hierarchically porous surface and the grafted –NH₂ groups, TAPI-DW demonstrated an exceptional adsorption capacity for the anionic azo dye Congo red (CR). The adsorption equilibrium was achieved within approximately 6 h, with a lower pH environment promoting removal efficiency. Coexisting ion experiments indicated that the introduction of Ca²⁺ ions dramatically enhanced the CR adsorption capacity from 168.71 mg·g⁻¹ to 301.14 mg·g⁻¹. This superior capture performance is attributed to the synergistic interplay of the aerogel’s aligned microchannels (derived from the native wood structure) for rapid mass transfer and the intensive chemical interactions, including electrostatic attraction, hydrogen bonding, and π-π stacking between CR molecules and the functional groups (–NH₂ and –OH) on the 3D skeleton. The Freundlich model fitting suggests a complex multilayer adsorption process on this heterogeneous wood aerogel surface. This work establishes a green and sustainable pathway for fabricating high-value biomass aerogel materials that show promise as candidates for the efficient remediation of dye-contaminated water. Further studies on reusability and long-term stability are needed to fully validate their potential for practical application.