Superelastic three-dimensional nanofiber-reconfigured spongy hydrogels with superior adsorption of lanthanide ions and photoluminescence

Materials combining high-water-content, robust mechanical performances, and multifunctionality, such as adsorption separation, photoluminescence and anti-fouling, are highly desirable for various applications. Electrospun nanofibrous hydrogels have emerged as attractive candidates; however, it has remained a great challenge to achieve these properties in three-dimensional (3D) bulk nanofibrous hydrogels. Here we report a facile and effective top-down approach to construct water-rich and superelastic 3D nanofiber-reconfigured spongy hydrogels (NRSHs) with hierarchically cellular architectures by combining sodium alginate/polyacrylamide (SA/PAM) electrospun nanofibers and the freeze-drying process of homogenized nanofiber dispersion, followed by chemically cross-linked with pyromellitic dianhydride (PMDA). The resulting SA/PAM NRSHs exhibit a comprehensive property of high water capacity, complete recovery from 80% strain, and stress retention of ∼90% after 100 compression cycles due to the synergistic effects of its cellular structures, well-hydrated and robust bonded nanofibrous skeleton. Furthermore, the well-designed NRSHs with abundant carboxyl groups perform superior adsorption behavior towards lanthanide ions (Ln3+) and excellent regenerability, the maximum equilibrium adsorption capacities for Eu3+ and Tb3+ reach up to 492.9 and 472.9 mg/g, respectively. Notably, benefiting from the typical 4f transition luminescence features of Ln, the obtained Ln3+-SA/PAM NRSHs are endowed with outstanding photoluminescent performance independent of compression deformation, tunable compression stress towards different Ln3+ concentration, desirable shapes and tunable emission color, simultaneously. The fabrication of such fascinating NRSHs will provide new prospects to design and develop multifunctional 3D bulk hydrogels for various applications, such as adsorbents, luminescent patterning, underwater fluorescent devices, sensors and bioengineering.