Multiphase surface growth of hydrophobic ZIF-8 on melamine sponge for excellent oil/water separation and effective catalysis in a Knoevenagel reaction

Here is reported the fabrication of a highly porous and hydrophobic melamine sponge based composite (MF-ZIF-8 sponge) with effective catalysis via the simple surface growth of ZIF-8 onto the strut surface of melamine sponge under the condition of the presence of polydopamine possessing a strong adhesive ability through noncovalent adsorption and covalent reaction. The successful integration of melamine sponge and ZIF-8 into one composite was confirmed using scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction and thermogravimetry. Combining the advantages of both materials, MF-ZIF-8 sponge with a high porosity, high hydrophobicity and low density showed excellent oil/water separation performance as its mass-based oil absorption capacity could reach up to 3800 wt%, which is much higher than that of pure ZIF-8. Besides its more effective catalysis compared to the corresponding pure ZIF-8 in a Knoevenagel reaction, since MF-ZIF-8 sponge can be easily separated from the organic liquid reaction mixture it is a potential candidate for the catalysis of various organic reactions.