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 similar to 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 (Ln(3+)) 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 Ln(3+)-SA/PAM NRSHs are endowed with outstanding photoluminescent performance independent of compression deformation, tunable compression stress towards different Ln(3+) concentration, desirable shapes and tunable