One-Step Green-Synthesized UiO-66-NH₂ /Alginate Composite Hydrogels with Improved Methylene Blue Adsorption

Zirconium-based metal-organic frameworks (Zr-MOFs) represent an important class of MOFs with high stability and outstanding properties, the green preparation and shaping of which are still challengeable works to hinder their real-world applications. In this presentation, UiO-66-NH₂ MOFs were in-situ grown accompanied by alginate (Alg) hydrogelation under aqueous conditions, achieving UiO-66-NH₂/Alg composite hydrogels. Relevant characterizations demonstrate the in-situ generated UiO-66-NH₂ MOFs were evenly distributed in hydrogel networks by attaching on Alg fiber surfaces. The network structure became denser, but both specific surface area and pore volume were augmented due to the presence of MOFs, which in turn increased active sites to interact with adsorbates. Thus, the adsorption capacity to methylene blue (MB) of composite hydrogels became higher with more dosage of MOF ligand, and the pH sensitivity of Alg adsorption to MB in the pH range of 4 to 10 was eliminated. Furthermore, the study of adsorption kinetics and isotherm reveals MB adsorption on the obtained hydrogels belong to rate controlling chemisorption mechanism. In summary, this manuscript presents a facile approach to realizing the green synthesis and shaping of Zr-MOFs by one-step compositing of UiO-66-NH₂ with Alg-based hydrogels in aqueous system, achieving MOFs-based composite hydrogels with enhanced MB adsorption.