Recent Advances in Sustainable Hydrogel-Based Functional Materials: Design Strategies, Functional Applications, and Future Perspectives

Hydrogel-based functional materials have garnered widespread attention across various fields due to their unique three-dimensional network microstructure and versatile, tunable properties. However, owing to the absence of a systematic analysis of the application mechanisms of hydrogels in diverse fields, accurately choosing the suitable type of hydrogel, its preparation method for specific application scenarios, and critical sustainability concerns still present challenges. A systematic framework connecting hydrogel design, functional performance, and sustainability is therefore needed. This review summarizes recent advances in chemical and physical cross-linking strategies and discusses their implications for material performance and environmental sustainability. Representative applications in separation engineering, sustainable agriculture, smart devices, and biomedical materials are evaluated from both functional and sustainability perspectives. Finally, key trade-offs between performance, functionality, scalability, and environmental impact are identified, and future directions toward sustainable-by-design hydrogel systems are proposed. This review aims to provide comprehensive theoretical references and technical insights for the development of sustainable hydrogel materials with more potential applications.