Facile Preparation of ZIF-67 Coated Melamine Sponge for Efficient Oil/Water Separation

In this work, an efficient oil/water separation system was constructed by a one-step method of coating ZIF-67 on melamine sponge through an in situ growing process without any bonding agent. ZIF-67 macroparticles were self-assembled onto the three-dimensional (3D) skeleton surface firmly, contributing to highly hydrophobic properties of the modified melamine sponge systems with a water contact angle (WCA) over 140°. The ZIF-67 coated hydrophobic melamine sponge (abbreviated as HMS-ZIF-67) exhibited excellent oil adsorption capacities. The obtained mass-based adsorption capacities ranged from 79 to 177 times its own mass. Due to the good elasticity and structural stability of HMS-ZIF-67, the adsorbed oil or solvents in the samples could be recycled in a simple squeezing process and the residual oil rate was below 22%, and also the adsorption capacity was almost invariable after 20 times of adsorption–desorption experiments. Moreover, HMS-ZIF-67 was capable of treating various surfactant-stabilized oil-in-water emulsions and separating oil from water effectively. This work provides a facile and economical method to prepare a hydrophobic melamine sponge and may also offer a strategy for constructing other 3D skeleton materials with highly hydrophobic properties.