Preparation of superhydrophobic melamine sponge by using heteroporous covalent organic framework and its application in efficient oil–water separation

Uncontrolled discharge of oily wastewater and frequent oil spill accidents poses significant threats to human health and ecosystems, incurring substantial economic costs. Therefore, there is an urgent demand for the development of efficient and sustainable oil–water separation technologies. This study presents a novel method for fabricating superhydrophobic melamine sponges for oil–water separation. This technique involves the deposition of a hydrophobic heteroporous covalent organic framework (HCOF) in conjunction with polydimethylsiloxane (PDMS) onto the sponge substrate, thereby forming MS@HCOF-PDMS. The HCOF modifies the hydrophilic nature of the sponge into a hydrophobic one while significantly enhancing its specific surface area, which enables superior oil adsorption performance. PDMS can effectively enhance the hydrophobicity of materials. The fabricated sponges exhibited water contact angles of 139.6° and 153.2° at PDMS concentrations of 0 % and 0.5 %, respectively. The superhydrophobic polyurethane sponge demonstrated adsorption capacities ranging from 78 to 147.35 g/g for organics and oils, and it maintained high-efficiency adsorption with minimal capacity loss after 10 cycles. Compared with MS @ single-pore COF-PDMS (MS @ SCOF-PDMS), the adsorption capacity of MS @ HCOF-PDMS is significantly improved. Notably, the adsorption capacity for peanut oil shows the most pronounced difference, with MS@HCOF-PDMS exhibiting a 37 % higher adsorption capacity than MS@SCOF-PDMS. Additionally, the adsorption capacities for other substances are approximately 15 % greater. By utilizing the superhydrophobic material developed in this study, the separation efficiency for dichloromethane from water can reach up to 99.3 %. These findings provide a promising strategy to develop advanced superhydrophobic materials for oil–water separation.