Peptide-mediated green synthesis of the MnO2@ZIF-8 core–shell nanoparticles for efficient removal of pollutant dyes from wastewater via a synergistic process

The MnO2@ZIF-8 core-shell nanoparticles for highly efficient dye degradation have been synthesized with a green method. ZIF-8 crystals with controlled morphology and size are first synthesized by using peptide to modulate the crystal growth. MnO2 is then coated on ZIF-8 via in situ reaction. The surface MnO2 density can be controlled by the dosage of KMnO4. The MnO2@ZIF-8 nanoparticles work as photocatalyst to degrade rhodamine B in a Fenton-like process, giving a degradation ratio of > 96.0%. The degradation kinetics comply well with the Pseudo-second-order model and the experimental equilibrium data meet the Langmuir model best. The specific hierarchical structure of MnO2@ZIF-8 assures a synergistic enhancement of the catalytic degradation performance from several aspects. First, anchoring of the MnO2 nanoparticles on ZIF-8 allows their well disperse to provide more active surface area. Second, highly porous ZIF-8 can adsorb dye molecules to accumulate them at the surface reactive sites. Third, the MnO2/ZIF-8 nano-heterojunctions enhance charge carrier transfer and accelerate the production of free oxidative radicals. The study demonstrates a green method for fabrication of hierarchical hybrid structures, paving the way for designing novel photocatalysts with potential applications for wastewater treatment.