A bio-inspired green method to fabricate pH-responsive sponge with switchable surface wettability for multitasking and effective oil-water separation

• A simple and environment-friendly method was proposed to prepare pH-responsive sponge. • The repeated wettability transition between superhydrophobicity and superhydrophilicity was achieved. • Driven by a pump, the sponge can achieve two opposite modes of continuous oil-water separation. • The sponge with switchable wettability can efficiently separate various oil-water mixtures by absorption or filtration. Smart oil-water separation materials with stimuli-responsive wettability surfaces have attracted wide attention. In this paper, a novel, simple and low-cost method is developed to prepare a pH-responsive melamine sponge (MS) with switchable wettability. This approach involves the hydrophobic modification of hexadecyltrimethoxysilane (HDTMS) on the MS surface modified by polydopamine (PDA) and the Michael addition reaction and Schiff base reaction between 12-aminododecanoic acid (NH 2 (CH 2 ) 11 COOH) and PDA. Hydrophobic/oleophilic HDTMS and pH-triggered NH 2 (CH 2 ) 11 COOH enable the functionalized sponge to repeatedly switch between the two extreme wettability under different pH environments. Benefiting from the excellent 3D porous surface structure and smart wettability, the as-prepared sponge can be applied in the on-demand separation of various oil-water mixtures by adsorption or filtration with a separation efficiency over 98.5% and high absorption capacity of 72.7–161.3 g·g −1 . With the assistance of pump-driven, continuous adsorption separation can be achieved in two cases by utilizing the wettability transformation. Moreover, in an alkaline solution, the sponge can quickly release most of the absorbed oil, showing a controllable desorption process. This smart wettability material with simple preparation and green has application potential in controllable oil-water separation and on-demand oil-spills treatment.