Rock-gravel-Moss inspired bifunctional MOF-based melamine sponge for superhydrophobic, triple-functional purification: Efficient oil-water separation, demulsification, and anion-cation adsorption

To address the challenge of synergistic treatment of oily wastewater and dye-containing textile effluent, a multifunctional melamine sponge (MTS/ZIF-8@Ce-MOF/MS) inspired by the “rock-gravel-moss” hierarchical structure was presented. A stable MOF-on-MOF heterostructured roughness was constructed through the sequential in situ growth of Ce-MOF and ZIF-8, followed by modification with a fluorine-free silane (MTS), successfully endowing the sponge with superhydrophobicity (WCA of 158°). Molecular dynamics simulations elucidated the molecular origin of this selective wettability, revealing the fundamental driving forces behind the efficient oil-water separation. The modified sponge demonstrated outstanding triple purification capabilities. Its superhydrophobic nature enabled a high saturation adsorption capacity of up to 91.35 g·g −1 for various oils (chloroform) with a separation efficiency >99% and 97.8% capacity retention after 20 cycles. Concurrently, it exhibited efficient demulsification ability for oil-in-water emulsions, increasing the emulsion transmittance by 115–177%. Furthermore, based on the synergistic adsorption mechanism of ZIF-8 and Ce-MOF, it achieved a high removal rate of 94.6% for both anionic and cationic dyes. This work not only provides a high-performance material for the integrated purification of complex wastewater but also offers new insights for the design of environmentally benign, multifunctional MOF-based composite materials.