In situ self-assembly synthesis of ZIF-8-poly(acrylamide-co-vinylimidazole)/sodium alginate composite hydrogel for Cu2+ removal.

Heavy metal ion pollution in wastewater, particularly Cu2+ contamination, threatens ecology and human health, demanding efficient adsorption materials in environmental remediation. However, conventional adsorbents suffer from insufficient capacity, poor mechanical stability, weak selectivity, and low reusability, restricting their practical application. Herein, a semi-interpenetrating network composite hydrogel (ZIF-8-AVA) was fabricated via in situ self-assembly, integrating ZIF-8 nanocrystals into a poly(acrylamide-co-vinylimidazole)/sodium alginate (AVA) matrix. Vinylimidazole units served as nucleation anchors, firmly immobilizing ZIF-8 on the polymer backbone via metal-ligand coordination to form a stable system. ZIF-8 significantly enhanced AVA's mechanical properties and Cu2+ adsorption performance: the composite followed the Langmuir monolayer adsorption model with a maximum adsorption capacity of 355.9 mg/g, achieving 93.81% Cu2+ removal efficiency at an initial concentration of 50 mg/L. Furthermore, the ZIF-8-AVA hydrogel exhibited excellent selectivity for Cu2+ in multi-competing-ion systems and maintained high adsorption efficiency after 5 consecutive adsorption-desorption cycles. The key innovation lies in the in situ self-assembly strategy that realizes the intimate integration of ZIF-8 with the hydrogel matrix via coordination-driven anchoring, overcoming the common issue of MOF particle leaching and synergistically enhancing adsorption capacity, selectivity, and mechanical stability. This work offers a novel approach for tunable MOF hydrogels, with great potential in heavy metal wastewater treatment.